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The thermometer read 121 degrees Fahrenheit when 71-year-old Steve Curry collapsed outside a restroom in Death Valley National Park last summer. Curry, who’d reportedly been hiking on a nearby trail in Golden Canyon, was just trying to make it back to his car. The National Park Service and the Inyo County Sheriff’s Office quickly responded to the scene. They tried to revive him with an external defibrillator, but it was not enough, and the medical helicopter that could’ve transported him to a hospital wasn’t able to take off because of the extreme heat. It was too late.

One of the last photographs of Curry alive, taken by a Los Angeles Times team on the day he died, shows him sitting under a tiny patch of shade, a large sun hat on his head and his face smeared with sunscreen. When asked by the Times why he was hiking that day, the experienced hiker replied, “Why not?”

This summer, millions of visitors will descend on national parks. They may not realize that extreme heat is not only making the outdoors riskier, but also making rescuing those in danger much more difficult. Park rangers in Death Valley respond to overheated visitors multiple times a week in the summer months, and in recent years, heat has been a factor in one to three deaths there a year. High temperatures can lead to heat exhaustion and heatstroke—conditions that can necessitate a search-and-rescue operation or an air ambulance, which can reach you quicker than an ambulance on the ground. But temperatures above 120 degrees Fahrenheit (a common summer occurrence in Death Valley) make the air too “thin” to give an ambulance helicopter the lift it needs to get off the ground and safely stay there.

Without a helicopter, rescuers on the ground—braving the same blistering heat—are the only option. Although park rangers want to help, park managers will not allow them to put their lives in danger for lengthy search-and-rescue operations in extreme heat. On-foot searches for people whose location is unknown are less likely to happen when temperatures are 120 degrees or hotter in Death Valley, though park rangers will respond to medical emergencies that they can safely get to (in developed areas and along roads, for example), even in high temperatures.

These rescue challenges are likely to become more and more common at numerous national parks. Some of the most popular—Death Valley and Joshua Tree in California, Big Bend in Texas, Grand Canyon in Arizona—are in desert regions where summer is just naturally, well, hot. Death Valley once reached an air temperature of 134 degrees, at the aptly named Furnace Creek in 1913.

But even the hot places are getting hotter. In 2021, Death Valley broke its record for most consecutive days over 125 degrees; projections from a report prepared for the National Climate Assessment show that temperatures across the southwestern United States will continue to warm above previous averages throughout the rest of the century. National parks (in part because of their locations in Alaska, at high elevations, and in the arid Southwest) are disproportionately affected by climate change—from 1895 to 2010, their temperatures increased at double the rate of the rest of the country, according to research published in 2018. Last June and July, at least five people—including Curry—died in national parks in the Southwest. Heat was a contributing factor in all five deaths.

But the heat doesn’t seem to be deterring visitors. In fact, record-breaking temperatures can even be a draw. In Death Valley, many visitors are eager to get a photo in front of the park’s giant digital thermometer with its eye-popping numbers in the triple digits.

Visiting a national park is a quintessential American pastime, particularly in the summer. But in recent years, the experience of visiting a park, and other outdoor destinations, has changed alongside the climate. A study led by the NPS predicted a significant uptick in heat-related illness for its visitors in the coming years. “People should know that heat can kill, and it does,” Abby Wines, a Death Valley National Park spokesperson, told me.

Rangers and volunteers in the Grand Canyon, where hikers start the day going down and must exert themselves more on the way back up, when temperatures are higher, have since 1997 implemented a proactive approach. A “preventive” search-and-rescue team stops people before they’ve reached the canyon’s bottom, and checks on their water supplies, educates them on the day’s forecast, and encourages a U-turn if necessary.

Hikers can also take their own precautions to get ahead of an emergency. Recommendations are commonsense and easy to follow wherever you are: Drink water, shorten your activities, wear a hat, eat salty snacks, and seek out shady trails if possible. Don’t discount temperatures of 105 or 110 degrees, Wines warned, even though those numbers are “not so hot” by Death Valley standards. Low humidity in these dry places means your sweat evaporates off your body as it’s being created, getting rid of a familiar signal of exertion. And keep an eye on your watch: Hiking low-elevation trails after 10 a.m., and especially from 3 to 5 p.m., is discouraged in places like Death Valley.

Stop signs at the Golden Canyon trailhead, where Curry hiked the day of his death, warn visitors of extreme heat danger in nine different languages. Another sign shows a helicopter with a black line slashed through it, warning that a rescue may be hours away. When you see those signs, take heed.

Over the past two years, a simple but baffling request has preceded most of my encounters with medical professionals: “Rate your pain on a scale of zero to 10.”

I trained as a physician and have asked patients the very same question thousands of times, so I think hard about how to quantify the sum of the sore hips, the prickly thighs, and the numbing, itchy pain near my left shoulder blade. I pause and then, mostly arbitrarily, choose a number. “Three or four?” I venture, knowing the real answer is long, complicated, and not measurable in this one-dimensional way.

Pain is a squirrely thing. It’s sometimes burning, sometimes drilling, sometimes a deep-in-the-muscles clenching ache. Mine can depend on my mood or how much attention I afford it, and can recede, nearly entirely, if I’m engrossed in a film or a task. Pain can also be disabling enough to cancel vacations, or so overwhelming that it leads people to opioid addiction. Even 10+ pain can be bearable when it’s endured for good reason, like giving birth to a child. But what’s the purpose of the pains I have now, the lingering effects of a head injury?

The concept of reducing these shades of pain to a single number dates back to the 1970s. But the zero-to-10 scale is ubiquitous today because of what was called a “pain revolution” in the ’90s, when intense new attention to addressing pain—primarily with opioids—was framed as progress. Doctors today have a fuller understanding that they can (and should) think about treating pain, as well as the terrible consequences of prescribing opioids so readily. What they are learning only now is how to better measure pain and treat its many forms.

About 30 years ago, physicians who championed the use of opioids gave robust new life to what had been a niche speciality: pain management. They started pushing the idea that pain should be measured at every appointment as a “fifth vital sign.” The American Pain Society went as far as copyrighting the phrase. But unlike the other vital signs—blood pressure, temperature, heart rate, and breathing rate—pain had no objective scale. How to measure the unmeasurable? The society encouraged doctors and nurses to use the zero-to-10 rating system. Around that time, the FDA approved OxyContin, a slow-release opioid painkiller made by Purdue Pharma. The drugmaker itself encouraged doctors to routinely record and treat pain, and aggressively marketed opioids as an obvious solution.

To be fair, in an era when pain was too often ignored or undertreated, the zero-to-10 rating system could be regarded as an advance. Morphine pumps were not available for those cancer patients I saw in the ’80s, even those in agonizing pain from cancer nt their bones; doctors regarded pain as an inevitable part of disease. In the emergency room where I practiced in the early ’90s, prescribing even a few opioid pills was a hassle: It required asking the head nurse to unlock a special prescription pad and making a copy for the state agency that tracked prescribing patterns. Regulators (rightly) worried that handing out narcotics would lead to addiction. As a result, some patients in need of relief likely went without.

After pain doctors and opioid manufacturers campaigned for broader use of opioids—claiming that newer forms were not addictive, or much less so than previous incarnations—prescribing the drugs became far easier and were promoted for all kinds of pain, whether from knee arthritis or back problems. As a young doctor joining the “pain revolution,” I probably asked patients thousands of times to rate their pain on a scale of zero to 10 and wrote many scripts each week for pain medication, as monitoring “the fifth vital sign” quickly became routine in the medical system. In time, a zero-to-10 pain measurement became a necessary box to fill in electronic medical records. The Joint Commission on the Accreditation of Healthcare Organizations made regularly assessing pain a prerequisite for medical centers receiving federal health-care dollars. Medical groups added treatment of pain to their list of patient rights, and satisfaction with pain treatment became a component of post-visit patient surveys. (A poor showing could mean lower reimbursement from some insurers.)

But this approach to pain management had clear drawbacks. Studies accumulated showing that measuring patients’ pain didn’t result in better pain control. Doctors showed little interest in or didn’t know how to respond to the recorded answer. And patients’ satisfaction with their doctor’s discussion of pain didn’t necessarily mean they got adequate treatment. At the same time, the drugs were fueling the growing opioid epidemic. Research showed that an estimated 3 to 19 percent of people who get a prescription for pain medication from a doctor developed an addiction.

Doctors who wanted to treat pain had few other options, though. “We had a good sense that these drugs weren’t the only way to manage pain,” Linda Porter, the director of the National Institutes of Health’s Office of Pain Policy and Planning, told me. “But we didn’t have a good understanding of the complexity or alternatives.” The enthusiasm for narcotics left many varietals of pain underexplored and undertreated for years. Only in 2018, a year when nearly 50,000 Americans died of an overdose, did Congress start funding a program—the Early Phase Pain Investigation Clinical Network, or EPPIC-Net—designed to explore different types of pain and find better solutions. The network connects specialists at 12 academic specialized clinical centers, and is meant to jump-start new research in the field and find bespoke solutions for different kinds of pain.

A zero-to-10 scale may make sense in certain situations, such as when a nurse uses it to adjust a medication dose for a patient hospitalized after surgery or an accident. And researchers and pain specialists have tried to create better rating tools—dozens, in fact, none of which was adequate to capture pain’s complexity, a European panel of experts concluded. The Veterans Health Administration, for instance, created one that had supplemental questions and visual prompts: A rating of 5 correlated with a frown and a pain level that “interrupts some activities.” The survey took much longer to administer and produced results that were no better than the zero-to-10 system. By the 2010s, many medical organizations, including the American Medical Association and the American Academy of Family Physicians, were rejecting not just the zero-to-10 scale but the entire notion that pain could be meaningfully self-reported numerically by a patient.

In the years that opioids had dominated pain remedies, a few drugs—such as gabapentin and pregabalin for neuropathy, and lidocaine patches and creams for musculoskeletal aches—had become available. “There was a growing awareness of the incredible complexity of pain—that you would have to find the right drugs for the right patients,” Rebecca Hommer, EPICC-Net’s interim director, told me. Researchers are now looking for biomarkers associated with different kinds of pain so that drug studies can use more objective measures to assess the medications’ effect. A better understanding of the neural pathways and neurotransmitters that create different types of pain could also help researchers design drugs to interrupt and tame them.

Any treatments that come out of this research are unlikely to be blockbusters like opioids; by design, they will be useful to fewer people. That also makes them less appealing prospects to drug companies. So EPICC-Net is helping small drug companies, academics, and even individual doctors design and conduct early-stage trials to test the safety and efficacy of promising pain-taming molecules. That information will be handed over to drug manufacturers for late-stage trials, all with the aim of getting new drugs approved by the FDA more quickly.

The first EPICC-Net trials are just getting under way. Finding better treatments will be no easy task, because the nervous system is a largely unexplored universe of molecules, cells, and electronic connections that interact in countless ways. The 2021 Nobel Prize in Physiology or Medicine went to scientists who discovered the mechanisms that allow us to feel the most basic sensations: cold and hot. In comparison, pain is a hydra. A simple number might feel definitive. But it’s not helping anyone make the pain go away.

Summer has only just officially begun, and the world is already sweltering. This week, two counties in northwestern Maine were under their first-ever excessive-heat warning—part of a record-breaking “heat dome” that has settled on the eastern part of the country. Washington, D.C., might hit its first triple-digit high since 2016. Globally, the temperatures this spring have been even more shocking. Last week, the Sonoran Desert hit 125 degrees, the highest recorded temperature in Mexican history. Mecca, in Saudi Arabia, hit that same temperature. Last month, part of New Delhi, India, soared above 120 degrees.

These triple-digit highs are alarming and dangerous. In Mecca, hundreds of pilgrims making the Hajj pilgrimage to the holy Islamic city reportedly died in the heat. But in isolation, such temperatures can also be misleading. Not all 100-degree days are the same. The highest daily temperature isn’t the most revealing number about what a heat wave actually feels like, or what it does to our bodies.

One of the most destructive parts of a heat wave is not the highest highs, but the lowest lows. In other words, what’s worrisome isn’t just the daytime peaks but also the nighttime troughs. That’s because our bodies need the chance to cool off at night, recovering from the exertion of trying to keep us cool during hot days. But when temperatures stay high with no meaningful nighttime respite, that’s when the trouble really starts, Lisa Patel, a pediatrician and the executive director of the Medical Society Consortium on Climate and Health, told me.

Your heart pumps blood to the periphery of your body to cool down, eventually circulating it back to our hearts. But if it’s too hot at night, your heart just beats faster and faster trying to keep up, without a break before resuming such strenuous effort the next day. “These hearts just tire out, essentially,” Patel said. What counts as “too hot” is hard to say. One study found that deaths increased by 10 percent when temperatures stayed above 77 degrees Fahrenheit at night. The National Weather Service considers nights with a heat index (heat plus humidity) above 75 degrees, coupled with two days of highs at or above 105 degrees, as worthy of an “excessive heat warning” categorization.

Lingering nighttime heat is primarily a problem for people without air-conditioning or other ways to cool themselves off. If it’s 90 degrees outside but you’re nestled under a comforter with the AC set to 65, you’re likely just fine. Not everyone has that luxury, of course—and slightly cooler temperatures at night might spur penny-pinchers to turn off the AC.

Warmer nights are especially dangerous for older people, people with chronic conditions or heart disease, pregnant people, and children, who all have trouble regulating their body temperature. Newborns are particularly vulnerable: A study from the Catalonia region of Spain found that infants in the first week of life are particularly vulnerable to heat waves. City dwellers may also be especially at risk. They see hotter temperatures all throughout the day and night, as concrete and other urban structures absorb and re-emit more heat than natural surroundings. “It doesn’t get any better at night,” a Delhi rickshaw driver told CNN. On Tuesday, the city reported a nighttime temperature of 95 degrees, its hottest in more than a decade.

Besides nighttime temperatures, there’s another indicator to keep in mind: humidity. It plays a key role in how oppressive hot temperatures really feel, and how risky they are to our health. Humidity’s hazards come from how it can eliminate the effectiveness of sweating. If the air is already full of moisture, there’s nowhere for our sweat to evaporate. “Sweating is basically a sprinkler system,” Patel said. “Humid heat is much more dangerous to us because it takes away the one built-in mechanism we have to cool down.”

You might already be looking at temperatures that factor in humidity without knowing it. Heat combined with humidity creates a heat index, often referred to as the “real feel” temperature on weather forecasts. But an even better measure of heat and humidity is something called the “WetBulb Globe Temperature,” or WBGT, which combines measurements of temperature, relative humidity, wind speed, and sunlight, using readings from three thermometers. Confusingly, one of those measurements is what’s called a “wet bulb” temperature—a separate indicator from the WBGT.

Unlike traditional temperature readings, which are calculated in the shade, the WBGT more accurately represents what it might feel like to be working outside in exposed conditions during a heat wave, and better accounts for how well sweat can evaporate. The U.S. military postpones nonessential physical activity at a WBGT reading of 90 degrees Fahrenheit. As of midday Friday, large swaths of the Midwest and mid-Atlantic regions had WBGT readings in the mid-80s, which the National Weather Service considers high-to-extreme. Air temperatures, meanwhile, were in the mid-90s. (WGBT is generally, but not always, lower than the regular temperature.)

That’s not all to say that dry heat in the middle of the day can’t be dangerous, too. Dehydration can occur within half an hour in high temperatures. But higher wet-bulb temperatures or higher nighttime temperatures can make hot days even more dangerous. If at night it’s hot and humid, your body is under even more strain just trying to maintain a healthy temperature.

If people want to be best prepared for heat waves, the top-line temperature on the weather forecast doesn’t cut it. Heat is already the leading weather-related killer in the U.S., responsible for more deaths than hurricanes, floods, or tornadoes. And temperatures are getting hotter. Overnight lows in the U.S. are rising twice as fast as daytime highs, according to a 2022 Climate Central analysis. The problem isn’t just what numbers we check, but how heat policies account for them. Phoenix—America’s hottest and fastest-growing city—extended hours for some cooling shelters this year. But only two will be open overnight. People don’t need to die during heat waves. Ensuring they don’t will be an easier task if heat is measured in the right way.

Every meal I make begins with a single choice: extra-virgin olive oil or canola? For as long as I’ve cooked, these have been my kitchen workhorses, because they’re versatile, affordable, and—most of all—healthy. Or so I thought.

These days, every trip to the grocery store makes me second-guess myself. Lined up next to the bottles of basics such as canola, vegetable, and corn oil are relatively exotic—and expensive—options: grapeseed oil, pumpkin-seed oil, walnut oil. Some are labeled with technical-sounding terms such as “high-oleic,” “cold-pressed,” and “expeller-pressed.” There’s “hexane-free” coconut oil and “naturally refined” avocado oil—if you can make any sense of what these labels mean. Picking an olive oil alone is like trying to plan a European vacation: Greece, Italy, or Spain? Or how about a Mediterranean blend?

The confusion doesn’t end at the checkout counter. Concerns about the smoke point of various oils have prompted terrifying headlines such as “What You Need to Know About Cooking Oils and Cancer.” There are countless guides to selecting the best oil for specific styles of cooking, which discuss distinctions between deep and shallow frying, and the pros and cons of processed oils. And trepidation around “seed oils,” a group that includes common options such as canola, soybean, and corn, has recently gone mainstream: Last year, the national salad chain Sweetgreen announced that it would stop using the oils altogether, citing customer concerns about their healthiness.

Health concerns seem to abound about practically every oil available. So what on earth are we supposed to cook with? “People get truly suffocated by all those details,” Penny Kris-Etherton, a professor emerita of nutrition at Penn State University, told me. Obsessing over the nutritional benefits of cooking oil won’t drastically improve anyone’s diet. In fact, at a certain point, it becomes a distraction from eating well.

You can’t cook without oil or other kinds of fat—or, at least, cook well. Oil is primarily a vehicle for heat; without it, perfectly seared steak, caramelized onions, and crispy potatoes wouldn’t exist. Oil adds flavor too: Extra-virgin olive oil imparts richness to a caprese salad, and a drizzle of sesame oil transforms boiled greens into a savory side dish.

But consuming certain oils and other kinds of fats can be harmful for your health. Whatever oil, or oils, you keep in your kitchen you’ll probably consume in large amounts, so putting some thought into picking a healthy one is worthwhile.

One distinction matters most. Saturated fats, which tend to be solid at room temperature and include butter and lard, are linked to an increased risk of death from all causes, including heart disease and cancer. Their unsaturated kin, usually liquid at room temperature and typically derived from plants, are considered far healthier, because they can lower cholesterol and reduce the risk of heart disease. “What we really want to do is replace the saturated fat in our diets with unsaturated fats,” Kris-Etherton said.

This idea has greatly influenced the oil aisle: You don’t see unhealthy solid fats such as lard and tallow much anymore, and most artificial trans fats were banned in 2015. “We’ve improved the fats in the U.S. food supply a lot in the last 20 years,” Walter Willett, a nutrition professor at Harvard, told me. “What’s left of the liquid plant oils are basically all healthy.”

Let this reassure you: Olive oil is always a good idea, but pretty much all other oils are too. Most plant-based oils contain so-called monounsaturated fatty acids and polyunsaturated fatty acids (PUFAs), which are genuinely good for you. (Maybe you’ve heard of the golden child of PUFAs: omega-3.)

Yes, even seed oils. Fears about these oils are fueled by another PUFA: omega-6, which has a complex link to inflammation. Because seed oils contain omega-6, detractors have claimed that cooking with them can cause many illnesses driven by inflammation, and that it competes with omega-3, diminishing the latter’s benefit. The reality is more nuanced: Omega-6 is associated with some inflammation, but consuming it is also linked to a reduced risk of heart disease and cancer. It does compete with omega-3, but not significantly, Willett told me. Besides, framing these fatty acids as being in opposition is counterproductive. “We need both,” he said.

If seed oils are unfairly vilified, the health properties of certain other oils get too much attention. Polyphenols, compounds known for being great antioxidants and anti-inflammatory molecules, are abundant in olive oil, especially those that have been minimally processed. Labels describing heatless methods for extracting oil, such as “cold-pressed” or “expeller-pressed,” or highlighting a lack of processing, such as “unfiltered” or “unrefined,” are meant to convey an abundance of healthy bioactive molecules. These aspects are worth considering, but they won’t make or break the healthiness of an oil. If it’s unsaturated, any oil is fine, “as long as people use them properly,” Ana Baylin, a nutrition professor at the University of Michigan, told me.

If any concern is worth paying attention to, it’s how to use oil well. Past its smoke point—the temperature at which an oil begins smoking—oil breaks down into harmful by-products. Overheating butter, which has one of the lowest smoke points of all cooking fats, leads to a kitchen full of fumes, and food that has potentially harmful compounds. Frying chicken in extra-virgin olive oil, which has a moderately high smoke point (though low compared with other neutral oils), might be less dangerous—albeit expensive. Overheated oil usually isn’t a problem in home cooking, Willett said, though it can be in commercial deep-fried foods, including those sold at fast-food chains. At home, the more common issues are reusing old oil and storing Costco-size jugs of it for long periods of time, which also creates hazardous by-products (and rancid odors).

For such a basic ingredient, oil can be complicated. But in getting hung up on the minutiae of cooking oil, it’s easy to lose the plot. All of this quibbling may be about optimizing nutrition, but it’s a distraction from the goal: health. If you’re deciding on a good oil to use for a chocolate cake, Kris-Etherton said, “that’s not the issue.” Using the right oil for deep-frying might avoid creating carcinogenic compounds, but it won’t negate the health impacts of eating deep-fried foods. Conversely, “bad” oils can be used in healthy ways. Even saturated fat can be reasonable in the right context. “Fat makes food taste better,” Willett said. If a pat of butter entices someone to eat a wider variety of vegetables and whole grains, its benefits may outweigh the costs. (The foundation of French cuisine is butter, but France has lower heart-disease mortality rates than most other G20 countries. The simplest explanation is that the French eat relatively small portions, Baylin said.)

Cooking oil is hardly the only food that has generated disproportionate levels of nutritional discourse. Minor health aspects of practically every food—sweeteners, caffeine, protein—are constantly surfaced and debated, fueled by an endless cycle of nutrition research and media coverage, and turbocharged by wellness influencers. Those discussions can sometimes lead to meaningful insights. But more often, they’re just confusing. Unless every other aspect of your diet has been optimized to be as nutritious as possible, it probably doesn’t matter if you exclusively cook with extra-virgin olive oil that’s cold-pressed, unfiltered, and imported straight from a pristine Greek island. But hey, if you do, it’ll probably taste amazing.

This article was originally published by Undark Magazine.

When Ina Chung, a Colorado mother, first fed packaged foods to her infant, she was careful to read the labels. Her daughter was allergic to peanuts, dairy, and eggs, so products containing those ingredients were out. So were foods with labels that said they “may contain” the allergens.

Chung felt like this last category suggested a clear risk that wasn’t worth taking. “I had heard that the ingredient labels were regulated. And so I thought that that included those statements,” Chung says. “Which was not true.”

Precautionary allergen labels like those that say “Processed in a facility that uses milk or may contain fish” are meant to address the potential for cross-contact. For instance, a granola bar that doesn’t list peanuts as an ingredient could still say they may be included. And in the United States, these warnings are voluntary and not regulated; companies can use whatever precautionary phrasing they choose on any product. Some don’t use any labels, even in facilities where unintended allergens slip in; others list allergens that may pose little risk. Robert Earl, the vice president of regulatory affairs at the nonprofit Food Allergy Research & Education, or FARE, has even seen labels that include all nine common food allergens. “I would bet my bottom dollar not all of those allergens are even in the facility,” he says.

So what are the roughly 20 million people with food allergies in the U.S. supposed to do with these warnings? Should they eat that granola bar or not?

Recognizing this uncertainty, food-safety experts, allergy advocates, policy makers, and food producers are discussing how to demystify precautionary allergen labels. One widely considered solution is to restrict warnings to cases where visual or analytical tests demonstrate that there is enough allergen to actually trigger a reaction. Experts say the costs to the food industry are minimal, and some food producers across the globe, including in Canada, Australia, Thailand, and the United States, already voluntarily take this approach. But in the U.S., where there are no clear guidelines to follow, consumers are still left wondering what each individual precautionary allergen label even means.

Pull a packaged food off an American store shelf, and the ingredients label should say if the product intentionally contains one of nine recognized allergens. That’s because, in 2004, Congress granted the FDA the power to regulate labeling of eight major food allergens: eggs, fish, milk, crustaceans, peanuts, tree nuts, soybeans, and wheat. In 2021, sesame was added to the list.

But the language often gets murkier further down the label, where companies may include precautionary allergen labels, also called advisory statements, to address the fact that allergens can unintentionally wind up in foods at many stages of production. Perhaps wheat grows near a field of rye destined for bread, for instance, or peanuts get lodged in processing equipment that later pumps out chocolate-chip cookies. Candy manufacturers, in particular, struggle to keep milk out of dark chocolate.

Because the declarations are voluntary, the FDA offers no labeling guidance beyond saying that “advisory statements should not be used as a substitute for adhering to current good manufacturing practices and must be truthful and not misleading.”

Companies can choose when to use these warnings, which vary widely. For example, a 2017 survey conducted by the FDA and the Illinois Institute of Technology of 78 dark-chocolate products found that almost two-thirds contained an advisory statement for peanuts; of those, only four actually contained the allergen. Meanwhile, of 18 bars that carried no advisory statement for peanuts specifically, three contained the allergen. (One product that was positive for peanuts did warn more generally of nuts, but the researchers noted that this term is ambiguous.) Another product that tested positive included a nut warning on one lot but not on another. Individual companies also select their own precautionary-label phrasing.

For consumers, the inconsistency can be confusing, says Ruchi Gupta, a pediatrician and the director of the Center for Food Allergy & Asthma Research at Northwestern University’s Feinberg School of Medicine. In 2019, Gupta and her colleagues asked approximately 3,000 U.S. adults who have allergies, or care for someone who does, about how different precautionary-allergen-label phrases make a difference when they are considering whether to buy a particular food. About 85 percent said that they never purchase products with a “may contain” warning. Fewer than half reported avoiding products with labels suggesting that they were manufactured in a facility that also processes an allergen, even though some studies suggest that the wording of a precautionary allergen label does not always reflect the actual risk level. “People are making their own decisions on what sounds safe,” Gupta says.

[Read: Is it really safe to give babies peanut butter?]

When Chung learned that advisory labels are unregulated, she experimented with ignoring them when her then-toddler really wanted a particular food. When her daughter developed hives after eating a cereal labeled “May contain peanuts,” Chung went back to heeding warnings of peanut cross-contact but continued ignoring the rest.

“A lot of families just make up their own rules,” she says. “There’s no way to really know exactly what you’re getting.”

Most countries don’t regulate precautionary allergen labels, but many food-safety experts are exploring how they could. One popular tactic hinges on thresholds: the smallest amount of an allergen that could prompt an allergic reaction. If food producers abide by thresholds, the theory goes, they could restrict labels to products that contain allergens at or above this level.

Allergen sensitivities vary widely. To determine thresholds that would protect most people, researchers combine data from thousands of individual oral food challenges, in which an allergist presents a patient with increasing doses of an allergen until they have a reaction or have consumed a meal-size portion.

In 2022, an expert committee convened by the United Nations’ Food and Agriculture Organization (FAO) and the World Health Organization established thresholds for key allergens; the large majority of consumers with food allergies would not react at levels below these thresholds. The list initially included all allergens recognized in the U.S. except soy, and additionally broke tree nuts into specific examples—walnut, pecan, cashew, pistachio, almond, hazelnut. In 2023, the committee also established thresholds for additional allergens such as celery and soy.

That year, the committee also made recommendations on how policy makers could use the thresholds to regulate precautionary allergen labels. “It is critical that companies incorporate appropriate quality control, hygiene and risk mitigation practices into their overall allergen control programs,” Joseph Baumert, an FAO/WHO expert committee member, wrote in an email. Baumert is the director of the Food Allergy Research and Resource Program, an industry-funded consortium between the University of Nebraska at Lincoln and more than 100 member companies.

Companies, the recommendations suggest, should then be required to quantify the unintended allergens in products. This could include visual inspections for allergens such as whole sesame seeds, and using laboratory techniques to determine how much protein from an allergen is present. Taking into account how much of a food a person is likely to eat, the food producer should then determine whether an allergen’s concentration exceeds the recommended threshold-based limit; products with concentrations higher than this limit would have a label, whereas others would not. And all of the labels would need a single, standardized phrase.

A system like this “would be helpful for so, so many,” Chung says.

The FAO/WHO’s Codex Committee on Food Labelling, which helps set international food-labeling standards, may use the recommendations in developing its guidance on precautionary allergen labels. If adopted, many countries will follow the recommendations, predicts Marjan van Ravenhorst, who directs Allergenen Consultancy B.V. in the Netherlands.

But some companies already use thresholds for precautionary labels through the Voluntary Incidental Trace Allergen Labelling Program. Though VITAL was developed in Australia and New Zealand, companies headquartered in many countries, including the U.S., Canada, the United Kingdom, France, South Africa, and Thailand, have also subscribed, according to the food-safety specialist Jasmine Lacis-Lee, the president of the board of directors for Allergen Bureau, an industry-operated not-for-profit that runs the voluntary labeling program. In Switzerland, precautionary allergen labels are required when an allergen’s protein levels reach a concentration greater than 1,000 parts per million. Japan requires companies to list unintended allergens on the ingredients list itself whenever they are detected above an exceedingly low threshold.

Meanwhile, in the Netherlands, a mandatory threshold-based system will become fully enforced in 2026, and will require advisory labels when allergen concentrations surpass the thresholds recommended by the FAO/WHO committee. If there is no risk of an allergen, companies will not be able to use precautionary allergen labels.

A threshold-based approach should not have a major impact on the cost of food production, Lacis-Lee says. When it comes to implementing a VITAL risk assessment, she adds, “most businesses producing food should already be doing the vast majority of what is required.”

Exactly how often allergen testing is required under the threshold-based system depends on a facility’s risk level, says van Ravenhorst, who helped write the guidelines for the Netherlands’ new advisory-statement requirements: “If you only cut vegetables, and there is no allergen in your facility, it’s insane to test for different allergens every week.”

One concern about standardizing precautionary allergen labels is consumer comfort level. The FAO/WHO thresholds are designed to protect about 95 percent of an allergic population from an allergic reaction. Up to five percent could still react to allergens at levels so low that they fall under the threshold, at which point using a precautionary label would be against the rules. Of these individuals, some could experience mild to moderate anaphylaxis, but there are no confirmed reports of fatal anaphylaxis from allergens at or below the thresholds, according to the 2023 FAO/WHO report.

The report suggests that this system would improve safety for allergic consumers. Currently, unintended allergens can exist at higher levels without warning; with the proposed system, foods with allergens above the threshold would all carry a label.

Not offering a precautionary label when you know that an allergen is there, even at very low levels, can feel difficult, says van Ravenhorst, who herself has several allergies. But she feels that there’s a balance between overuse of labeling and protection: “We want to be informed when there is a real risk.”

Gupta’s team recently surveyed U.S. allergists for their thoughts on precautionary allergen labels, including whether thresholds should be used; a similar survey for people with allergies is in the works. Gupta wonders whether consumers might prefer a system in which each food label states whether allergens are entirely absent, present above a threshold, or present below a threshold. But she’s already concerned that this alternative would most benefit those who know their sensitivity levels from allergist visits, which may leave out many patients. Her research shows that low-income caregivers of children with allergies spend less on specialist appointments. She worries: “Will it cause a bigger divide?”

[Read: The overuse of allergy tests]

Some U.S. companies would likely welcome more guidance on advisory labeling, Baumert said. In keeping with the Food Safety Modernization Act, most already have allergen-control plans, which include monitoring for unintended allergens. Most food companies, for example, do some analytical work to confirm that their cleaning procedures are effective—for instance, when they switch from a recipe that contains an allergen to one that doesn’t.

But according to some companies, the current guidelines make it difficult to respond when producers are unable to eliminate traces of unintended allergens. Looking for a way out of a regulatory gray zone, some even opt to include allergens in recipes so that they can follow clearer guidelines. After Congress declared sesame a major food allergen in 2021, for example, the seed became a listed ingredient in many foods that people with sesame allergies previously enjoyed.

“This addition of sesame would likely not be needed if FDA would establish allergen thresholds or otherwise set forth clear guidance as to when advisory or precautionary labeling (i.e. “may contain” statements) may be used,” Eric Dell, the president and CEO of the American Bakers Association, wrote in a May 2023 letter to select congressional members.

When it comes to precautionary allergen labels, “we recognize that the extensive use of these statements may be confusing to consumers, and we are considering conducting some consumer research in this area,” an FDA spokesperson, Enrico Dinges, wrote in an email.

In January 2024, the FDA published draft guidance for the industry; in it, the agency acknowledged that there may be situations where food producers, even after following good allergen-management practices, cannot assure consumers that food is safe, and therefore should include labeling “that discloses the possible unintended allergen presence in the food.”

But the agency stopped short of universal recommendations on exactly how to determine whether an unintended allergen presents enough risk to warrant an advisory statement. There’s a need for clarity on the FDA’s expectations for precautionary allergen labels, Baumert said: “I think we’ve gotten further on an international basis than we have currently here in the U.S.”

Meanwhile, American families are left to interpret allergen-advisory labels alone. Chung’s daughter is now 6 years old, and the family no longer follows precautionary peanut labels. The change came after Chung learned of a 2021 review paper suggesting that half of people with peanut allergies can eat about half a peanut without reacting. Based on her daughter’s reaction history, Chung felt that her then-5-year-old could likely handle trace amounts too, because a severe allergic response seemed unlikely. So Chung took a chance and let her try a granola bar that her brother loved, despite the fact that the wrapper suggested it might contain peanuts. The response: no reaction. She really wanted it, Chung says, who recalls thinking: “If it’s safe, how wonderful would that be?

Nothing compares to the perfect summer run. All winter, even through spring, I sustain myself with the dream of jogging in shorts down a dry, grass-lined path, unencumbered by puddles or black ice. But that dream is becoming more elusive. Now, in mid-June, I already dread the prospect of being outside past about 7:30 in the morning. Summer is set to officially start on Thursday, and the coming season looks to be, once again, marred by record-breaking temperatures, prolonged heat waves, and devastating fires. As climate change pushes the environment to new and more frequent extremes, exercising outdoors in the spring and summer is getting—to use a technical term—grosser.

Summer has long been a time of year when people are more active, by as much as 20 percent, according to one study; millions of Americans camp, hike, jog, fish, or bike outside, taking advantage of the longer days, the respite from school, the riot of active wildlife and greenery. But being outdoors is starting to become synonymous with dangerous exposure, and the effects of the climate crisis appear to be reducing levels of physical activity around the world. Last summer in the U.S., hazardous air and sweltering temperatures closed hiking trails and cloistered campers indoors; marathons and triathlons—designed to push a notoriously stubborn bunch of athletes to their limits—were canceled too. And with the Summer Olympics in Paris fast approaching, some experts are worried about the toll of extreme heat—and about the strength of the contingency plans in current regulations and guidelines.

Based on the trajectory the world is on, summer extremes dangerous enough to compromise outside activities are “going to be happening more and more,” Carol Ewing Garber, an exercise physiologist at Columbia University, told me. People hoping to enjoy the outdoors will have to choose between chasing the perks of nature and minimizing exposure to new environmental extremes.

The clearest risk of exercising on hot days is heat stroke. When the body’s core temperature rises, toxins leak out of the gut, sparking inflammation throughout the body; the heart strains to deliver blood; the kidneys falter as fluid levels fall. What starts off as mild heat exhaustion—headaches and dizziness—can quickly transform into a serious bout of vomiting, delirium, cramps, and fainting, signs that the condition could soon turn fatal.

Each person’s threshold for too much heat, though, depends on factors such as baseline health, level of training, exertion, and precautions against overheating, Michael Sawka, an environmental physiologist at the Georgia Institute of Technology, told me. According to the National Weather Service, once the wet-bulb globe temperature—which takes into account humidity, wind, cloud cover, even the angle of the sun—crests above 90 degrees Fahrenheit, just 15 minutes of working or exercising in direct sunlight can seriously stress the body. For some official sporting events, such as road races—during which athletes go particularly long and hard—the American College of Sports Medicine (ACSM) has urged organizers to cancel or recommend voluntary withdrawal at wet-bulb temperatures above 82 degrees Fahrenheit. And because humidity stifles the ability of sweat to cool the skin, muggy days are a worry even when temperatures don’t seem that high—especially for populations with underlying health conditions. In New York, for instance, “anything above 80 [degrees], really, we kind of get concerned,” Sonika Patel, a cardiologist at NewYork-Presbyterian, told me.

Human bodies can also adapt to tolerate more heat—often, within just days. As people repeatedly expose themselves to higher temperatures, the amount of plasma in the blood increases, making it easier for the heart to shunt blood to the skin to dissipate heat; the sensors that trigger sweating recalibrate to make cooling more efficient. In laboratories, researchers frequently document athletes who have trained themselves to exercise with core body temperatures cresting regularly above about 105 degrees Fahrenheit. Still, these tricks aren’t cure-alls: The body can only produce so much sweat at a time, for instance.

Behavioral hacks to beat the heat have their limits too. Many guides for exercising during heat waves recommend tricks such as wearing airy clothing, working out in the shade, keeping hydrated, and scheduling activities to avoid the hottest hours of the day. But fabrics can get only so loose and light; shade isn’t always available or consistent; adequately hydrating requires heeding cues beyond thirst. And as average temperatures climb higher and higher, many of the mornings and evenings that offered respites from the heat are no longer cool enough to be comfortable. One day last summer, Phoenix logged a low of 97 degrees Fahrenheit.

Although some people certainly are taking these risks into account, when it comes to heat, “we often underestimate the impact on the body,” Garber told me; this can be especially true for those dead set on squeezing in a regular workout. And despite the ACSM’s guidelines, Tamara Hew-Butler, an exercise physiologist at Wayne State University, points out that canceling endurance events during heat is far from the default. Generally, she told me, the idea is to instead “just modify your training” to ready yourself for the heat. Even recreational sports leagues for kids will keep practices going in arguably dicey conditions.

The dangers of smoky days are in some ways clearer. There’s no question that exposure to pollutants comes with risk, especially for young kids, older people, and anyone already battling respiratory issues: Inhaling fine particulate matter can raise the risk of heart issues, lung disease, diabetes, and cognitive impairment; gases such as ozone can exacerbate asthma. Exercise, by definition a higher metabolic state, ups the rate at which those pollutants enter airways. And unlike the case with heat, there’s not much encouraging evidence to suggest that people can acclimate to working out healthfully in bad air, Michael Koehle, an environmental physiologist at the University of British Columbia, told me.

But balancing those risks with the benefits of outdoor activity is still a judgment call. Staying inside on a single horrendously smoke-choked day is a solid choice. The more summer days end up clogged with pollution, though, the hazier the long-term trade-offs of that decision become. Some researchers, such as Linsey Marr, an environmental engineer at Virginia Tech, err on the side of caution: Going off of the EPA’s color-coded air-quality index, she deems orange levels of air quality a “time to start scaling back.” At red, the next level up, “people should not exercise outdoors,” she told me.

Koehle, meanwhile, worries about going too strict. If pollutants shorten or cancel someone’s workout for a day or two, that’s not a huge deal, but periods of bad air quality can in some cases stretch into weeks and months. “The worst thing that can happen long term is that people cease to be active because they’re worried about the air quality,” Koehle told me. People who exercise outdoors may be exposed to some harmful substances in the short term. But it takes a while, he said, for the true health consequences to unfold, and in the meantime, they can still reap the physical and mental benefits of staying active. (One good way to strike a balance, he noted, is to focus on briefer, higher-intensity workouts.) Still, even Koehle draws a line with wildfires and other pollution events extreme enough that “you can’t see the sky,” he said. Certainly, purple, the next level up from red on the American air-quality index, is a clear cue to overhaul his fitness routine.

In some ways, working out indoors is the most straightforward answer to these conundrums. But gyms and home equipment are pricey, plenty of Americans don’t have air-conditioning, and indoor air quality can present its own concerns. And restricting activities to indoor venues automatically rules out recreation that’s designed to be—and, let’s face it, will always be better—outdoors. Indoor baseball stadiums exist but aren’t the norm, and just try floating the idea of moving an ultramarathon inside. If an inhospitable climate pushes people to revise their outdoor plans, some may give up on working out entirely—which may leave the population less prepared overall for more environmental extremes ahead. Staying fit is key to staving off many of the medical conditions that can make heat waves and pollution more dangerous. “One of the big recommendations we give people with cardiovascular-disease factors is to exercise more,” Patel told me. “But what if we see people who aren’t able to do that?”

The costs of these changes will be more than physical. Getting outdoors is also an opportunity for people to spend time with others, to breathe what fresh air is available, to soak up vitamin D, to experience nature in ways they can’t inside. For kids, especially, the outdoors are essential places to find communities. People who spend more time in green spaces think better and experience less stress. They have lower rates of anxiety and depression. My own itch to jog outside has never just been about the calorie burn or the steps; it’s about experiencing the world in ways I otherwise can’t. So far, I’ve been lucky in my pocket of New England. But I’m dreading the day when my perfect summer runs become fantasies that exist only in my head.

On New Year’s Day 2020, I was zipping up my fleece to head outside when the phone in the kitchen rang. I picked it up to find a reporter on the line. “Dr. Fauci,” he said, “there’s something strange going on in Central China. I’m hearing that a bunch of people have some kind of pneumonia. I’m wondering, have you heard anything?” I thought he was probably referring to influenza, or maybe a return of SARS, which in 2002 and 2003 had infected about 8,000 people and killed more than 750. SARS had been bad, particularly in Hong Kong, but it could have been much, much worse.

A reporter calling me at home on a holiday about a possible disease outbreak was concerning, but not that unusual. The press sometimes had better, or at least faster, ground-level sources than I did as director of the National Institute of Allergy and Infectious Diseases, and reporters were often the first to pick up on a new disease or situation. I told the reporter that I hadn’t heard anything, but that we would monitor the situation.

Monitoring, however, was not easy. For one thing, we had a hard time finding out what was really going on in China because doctors and scientists there appeared to be afraid to speak openly, for fear of retribution by the Chinese government.

In the first few days of 2020, the word coming out of Wuhan—a city of more than 11 million—suggested that the virus did not spread easily from human to human. Bob Redfield, the director of the Centers for Disease Control and Prevention, was already in contact with George Gao, his counterpart in China. During an early-January phone call, Bob reported that Gao had assured him that the situation was under control. A subsequent phone call was very different. Gao was clearly upset, Bob said, and told him that it was bad—much, much worse than people imagined.

“We don’t know what’s going on with this virus coming out of China right now,” I told the group assembled in a conference room at the National Institutes of Health. This was January 3, just 48 hours after the reporter had called me at home. The scientists sitting around the table, led by Vaccine Research Center Director John Mascola, knew what I was going to say next: “We are going to need a vaccine for whatever this new virus turns out to be.”

Among those present was Barney Graham, a gentle giant of a man at 6 feet 5 inches tall, and one of the world’s foremost vaccinologists. For years, Barney had been leading a group of scientists trying to develop the optimal immunogens for vaccines injected into the body. (An immunogen refers to the crucial part of any vaccine that generates the immune response.) They had been working with Moderna on a vaccine platform called mRNA, the result of groundbreaking research conducted over many years by Katalin Karikó and Drew Weissman, who would win the Nobel Prize in 2023. “Get me the viral genomic sequence,” Barney said, “and we’ll get working on a vaccine in days.”

At this point, an FDA-approved vaccine had never before been made using mRNA technology, and although a lot of skepticism remained, my colleagues and I were very optimistic about it. Compared with other vaccines, the mRNA process is faster and more precise. The team needed the coronavirus’s genomic sequence so that it could pick out the part that codes for the spike protein (the immunogen) and, together with Moderna, use it to make the correct mRNA.

[From the January/February 2021 issue: How science beat the virus]

Only a week later, on January 10, I received an excited phone call from Barney: Scientists had just uploaded the SARS-CoV-2 sequence to a public database. Barney then immediately contacted a company that produces artificial strings of genetic code. He placed an order for the nucleotide sequence, and this lifesaving product was delivered in a small test tube packaged in a FedEx envelope. The modest charge was put on a credit card.

But soon after, Barney made a sobering point: A full-blown vaccine effort, including clinical trials, was going to cost a lot of money, far beyond what was in the Vaccine Research Center’s budget. I told him not to worry. “If this thing really explodes, I promise you, I will get us more money. You just go and make your vaccine.”

About an hour into a meeting in the White House Situation Room on January 29, concerning how to evacuate U.S. citizens from Wuhan, President Donald Trump walked in. The first thing he did, to my great surprise, was look right at me.

stylized photo of many people sitting at long conference table in suits
Anthony Fauci briefs President Donald Trump in the White House Situation Room,
January 29. (Joyce N. Boghosian / White House)

“Anthony,” he said, “you are really a famous guy. My good friend Lou Dobbs told me that you are one of the smartest, knowledgeable, and outstanding persons he knows.” I gulped. Thus began my first extended conversation with the 45th president of the United States. A big, imposing man, Trump had a New York swagger that I instantly recognized—a self-confident, backslapping charisma that reminded me of my own days in New York. For the next 20 minutes, as we discussed the new virus, the president directed many of his questions my way. I had met Trump only once before. In September 2019, I had been part of a group invited to the Oval Office for the signing of an executive order to manufacture and distribute flu vaccines. Prior to that, I had sometimes wondered what it would be like to interact with him. He had shocked me on day one of his presidency with his disregard of facts, such as the size of the crowd at his inauguration. His apocalyptic inaugural address also had taken me aback, as had his aggressive disrespect for the press. But at that brief signing ceremony, I had found him far more personable than I’d expected. Of course, I had no idea in January 2020 what the months and years ahead would be like.

I had confronted other terrible outbreaks over the course of my career—HIV in the 1980s, SARS in 2002 and 2003, Ebola in 2014, Zika in 2015—but none of them prepared me for the environment I would find myself in during the coronavirus pandemic. The nation was and is extremely polarized, with a large portion of Americans reflexively distrustful of expertise. On social media, anyone can pretend to be an expert, and malicious information is easily amplified. Soon I would come to learn just how dangerous these conditions can be.

A code red went off in my mind during the week of January 23, when I saw photos in a newspaper showing that the Chinese government was quickly erecting a 1,000-bed prefabricated hospital. At that point, the virus had reportedly killed just 25 people and infected about 800, according to data the Chinese had released. Time out, I thought. Why would you need that many hospital beds when fewer than 1,000 people are infected? That was the moment I suspected we could be facing an unprecedented challenge, and my anxiety took a sharp turn upward.

A photograph of a prefabricated hospital in China.
Hundreds of construction workers erect a prefabricated hospital in Wuhan, January 28, 2020. (Getty)

By the very end of January, we were hearing that the cases in China were increasing by about 25 percent a day. Reportedly, more than 9,000 people were infected, and 213 people were dead. The number of infections in a single month had surpassed the 2002–03 SARS outbreak. The United States had discovered its first known case of this novel coronavirus on January 20; a 35-year-old man had returned home to Washington State from Wuhan with a severe cough and a fever. The CDC had already begun screening passengers at several U.S. airports, taking their temperature and asking them about symptoms such as a sore throat and a cough. We began to wonder: Should we recommend closing the United States to travelers from China? On January 31, seated in front of the Resolute desk, Health and Human Services Secretary Alex Azar, the CDC’s Bob Redfield, and I explained the details of a proposed travel ban to the president. He posed several questions specifically to me about whether I was fully on board with the ban. “It is an imperfect process with some downsides, Mr. President, but I believe it’s the best choice we have right now,” I told him. Later that day, the Trump administration announced that travel restrictions would go into effect.

The White House communications team began arranging for me to appear on news shows. The entire world was transfixed by this rapidly evolving outbreak, and I became the public face of the country’s battle with the disease. This was useful, in that I could both try to calm the country’s anxieties and provide factual information. But it also led to the gross misperception, which grew exponentially over time, that I was in charge of most or even all of the federal government’s response to the coronavirus. This would eventually make me the target of many people’s frustration and anger.

On February 11, the World Health Organization officially designated the disease caused by the novel coronavirus as COVID-19, which was now spreading relentlessly around the world. And in the midst of this, the CDC, the country’s premier public-health agency, was stumbling badly.

[From the September 2020 issue: How the pandemic defeated America]

The agency traditionally had a go-it-alone attitude, excluding input from outside sources. Its personnel were talented and deeply committed professionals. I respected them, and many were friends. But the CDC’s approach, which is based on tracking symptoms, was poorly suited to dealing with a swiftly spreading disease in which, it would later turn out, more than a substantial portion of the transmissions come from people who are asymptomatic. The CDC was slow to recognize and act on that.

Another vulnerability was the way the CDC was set up to collect data. Rather than obtaining data firsthand, the agency depended on public-health departments around the country—but those departments did not consistently provide complete, up-to-date data. Some provided information reflecting what had occurred weeks earlier, not the day before. As the disease kept spreading, what was actually happening was always far worse than what the CDC’s data were telling us at the time. Public-health officials had to constantly play catch-up.

The CDC had an outstanding track record for quickly creating tests for diseases like Zika. With COVID, however, instead of immediately partnering with the diagnostic industry, it started from scratch with a test that turned out to be defective. The agency then failed to fix the defect, and wasted even more time in developing adequate testing. February was a lost month as a result.

Although the CDC struggled, there was no mistaking the message delivered on February 25 by its director of immunization and respiratory diseases, Nancy Messonnier. She told reporters that a pandemic in the United States was no longer a matter of if but when, and that we should prepare to close schools and work remotely. “Disruption to everyday life may be severe,” she announced. Nancy did the right thing: She told Americans the truth. But not surprisingly, her statement caused a firestorm. The media erupted, and the stock market plummeted nearly 1,000 points. Trump was furious.

The next day, he announced that Vice President Mike Pence would take over for Alex Azar as the head of the White House coronavirus task force. I met Pence the day he ran his first task-force meeting. He was soft-spoken and always solicited the medical opinions of the physicians on the task force. He listened carefully to our answers, often asking astute follow-up questions and never pretending to understand something if he did not. But I also picked up on little things that indicated how differently this administration operated from previous ones. Vice presidents are always publicly loyal to the president; that is part of the job. But Pence sometimes overdid it. During task-force meetings, he often said some version of “There are a lot of smart people around here, but we all know that the smartest person in the building is upstairs.”

photo looking in through window at press room with man speaking and gesturing at lectern with camera and audience
Vice President Mike Pence addresses reporters in the White House briefing room, March 3. (The Washington Post / Getty)

Others joined Pence in heaping praise on Trump. When the task force held teleconferences with governors, most of the Republicans started by saying, “Tell the president what a great job he is doing.” But a couple of days after Nancy’s bombshell announcement, when I got a surprise phone call from Trump at 10:35 p.m., I did not flatter him. What I did do during our 20-minute conversation was lay out the facts. I encouraged him not to underplay the seriousness of the situation. “That almost always comes back to bite you, Mr. President,” I said. “If you are totally honest about what is happening with COVID, the country will respect you for it.” He was courteous to me, and as we hung up, I felt satisfied that he had heard what I’d said.

I was worried about community spread, and I was particularly focused on Seattle. A longtime colleague called me from the city on March 3 and told me that 380 people with flu-like symptoms had been screened in four emergency rooms. Four had tested positive for COVID, a roughly 1 percent infection rate—that may not sound like much, but it was a clear signal that the virus was spreading among those unaware that they had been exposed. That meant the 1 percent was only a tiny fraction of what was actually already happening. When I brought this information to the task-force meeting, neither Pence nor Treasury Secretary Steven Mnuchin seemed to fully appreciate the seriousness of what I was telling them. While I was warning them of the impending disaster, the president was declaring outright to the press that the situation was under control. Without deliberately contradicting him, I kept repeating that things would get worse, and indeed they did.

Then, in one Oval Office meeting, I mentioned to Trump that we were in the early stages of developing a COVID vaccine. This got his attention, and he quickly arranged a trip to the NIH. During his visit, Barney Graham told the president that within a couple of weeks, a Phase 1 trial would likely begin. The president asked, “Why can’t we just use the flu vaccine for this virus?” It was not the first or the last time that he seemed to conflate COVID with influenza.

People associate science with immutable absolutes, when in fact science is a process that continually uncovers new information. As new information is uncovered, the process of science allows for self-correction. The biological and health sciences are different from the physical sciences and mathematics. With mathematics, two plus two equals four today, and two plus two will equal four 1,000 years from now. Not so with the biological sciences, where what we know evolves and uncertainty is common.

On March 8, I appeared on a 60 Minutes broadcast in a segment about COVID. At one point, I told the interviewer, “Right now in the United States, people should not be walking around with masks.” I was expressing not just a personal opinion, but the consensus at the time—a view shared by the surgeon general and the CDC.

The supply of masks was already low. One fear was that there would be a stampede, and we would create an even greater shortage of masks needed by the health-care workers taking care of very ill COVID patients. Although there was accumulating evidence that the virus was spread by aerosol, this was not widely accepted, certainly not by the WHO. When additional information became available—including that the virus was readily spread by infected people who had no symptoms—we advised the public to wear masks. But this was how I became the public-health official who, very early in the pandemic, instructed people not to wear a mask. Later, my words would be twisted by extreme elements in an attempt to show that I and other scientists had misled the public, that we could not be trusted, and that we were flip-floppers.

What I came to realize is that our country is more profoundly divided than I’d ever understood. I remember a time when people expected diverse political opinions. You didn’t have to agree, but you respected one another enough to listen. Now the partisanship is so intense that people refuse to even try. They ignore facts in favor of tribal politics. That’s how you wind up with dangerous conspiracy theories. The controversy over masks illustrates a fundamental misperception of how science works. In reality, our understanding of COVID continually evolved, and our medical advice had to change to reflect this.

March 2020 was when COVID became frighteningly real to Americans. This was also around the time I started waking up with a jolt at 4 a.m. to stare at the ceiling with worry. I believe Trump thought that COVID would be temporary: A little time goes by, the outbreak is over, everyone goes back to work, and the election cycle can begin. He could not have imagined that the pandemic would go on for such a long time. I think this explains why he repeatedly asked me and others whether COVID resembled the flu. He desperately wanted the pandemic to disappear, just as flu does at the end of the flu season. Tragically, COVID was not the flu, and it did not vanish. Just the opposite. And so, with the ghastly reality setting in, Trump began to grab for an elixir that would cure this disease. Along came hydroxychloroquine.

Trump began hearing from the Fox News star Laura Ingraham and others who were promoting the drug as a COVID treatment. People have long taken hydroxychloroquine to prevent or treat malaria. It is also used to treat inflammatory and autoimmune diseases such as lupus and rheumatoid arthritis. Soon Trump began touting it to millions of worried Americans at our now-daily press briefings. But there were no clinical studies proving that this antimalarial drug would alleviate COVID. And it might even hurt people. The president seemed unable to grasp that anecdotes of how hydroxychloroquine might have helped some people with COVID did not translate into solid medical advice. This is when I realized that eventually, I would have to refute him publicly. This was not the White House I had known, and I’d been advising presidents since the Reagan administration. The differences were going to dramatically affect the way I could do my job. “Hydroxychloroquine doesn’t work,” I told reporters. After that, they would inevitably ask me if I agreed with something Trump had said, such as the idea that COVID would disappear “like a miracle.” I would then have to respond with the truth: “Well, that’s not going to happen.”

photo of back of Donald Trump leaving room past Fauci, standing and facing camera with arms crossed
Trump departs a daily coronavirus briefing, March 26. (Jonathan Ernst / Reuters / Redux)

I took no pleasure in contradicting the president of the United States. I have always had a great deal of respect for the Office of the President, and to publicly disagree with the president was unnerving at best and painful at worst. But it needed to be done. I take very seriously a statement in the first chapter of Harrison’s Principles of Internal Medicine, of which I have been an editor for 40 years: “The patient is no mere collection of symptoms, signs, disordered functions, damaged organs, and disturbed emotions. [The patient] is human, fearful, and hopeful, seeking relief, help, and reassurance.” This compels me to always be honest; to be unafraid of saying that I do not know something; to never overpromise; to be comforting, yet realistic. Admitting uncertainty is not fashionable in politics these days, but it is essential in my work. That’s the beauty of science. You make a factual observation. If the facts change, the scientific process self-corrects. You gather new information and data that sometimes require you to change your opinion. This is how we better care for people over time. But too few people understand the self-corrective nature of science. In our daily press conferences, I tried to act as if the American public were my patient, and the principles that guided me through my medical career applied.

There is a widely circulated photo of me from a White House press briefing on March 20, in which I put my hand to my forehead in response to a comment the president had made. That day, Trump was especially flippant. He was standing with Secretary of State Mike Pompeo, making one provocative statement after another. Then he said, “Secretary of State Pompeo is extremely busy, so if you have any questions for him right now could you do that because … I’d like him to go back to the State Department or, as they call it, the ‘Deep State’ Department.” I had a moment of despair mixed with amusement. I put my hand to my forehead to hide my expression. This is when things began to get difficult for my family and me.

In late March, officials monitoring the dark web started to see a considerable amount of hostility and threats directed toward me. The problem was that a hard-core group saw me as a naysaying bureaucrat who was deliberately, even maliciously, undermining Trump. They loved and supported the president and regarded me as the enemy. To them, my hand-to-forehead moment validated what they already believed about me.

photo of Fauci touching his forehead with his hand over face while standing
Fauci while Trump speaks at the March 20 coronavirus briefing (Erin Schaff / The New York Times / Redux)

As a result, I was assigned a security detail. For years, AIDS had made me a target, but that was largely before social media. Back then, I used to get one or two insulting letters a month, mostly homophobic rants, sent to my office at the NIH. Now my family and I were barraged by emails, texts, and phone calls. I was outraged that my wife, Christine, and our daughters were harassed with foul language and sexually explicit messages, and threatened with violence and even death. I was angry and wanted to lash out. But these direct expressions of hatred did not distract or frighten me. I did not have time for fear. I had a job to do.

My training as a physician in a busy New York City hospital had taught me to push through crises and fatigue, to not feel sorry for myself. During the pandemic, Christine also insisted that I balance the demands of work with taking care of myself. (“You are going to bed at a decent hour, you are going to eat regular meals, and you are going to carry a water bottle,” she said in a way that left no room for argument.) Her advice helped me get through everything that followed.

But in the ensuing years, I also came to realize that addressing the root cause of our country’s division is beyond my capabilities as a scientist, physician, and public servant. That doesn’t mean I’ve given up hope that the country can be healed. I believe scientific education is more crucial now than it has ever been in American history. Children should learn what the scientific process is, how it works, and that it self-corrects. Most of all, I believe we need to reclaim civility. To do so, we need to understand that we’re all more alike than we are different—that we share common goals for ourselves and for our communities. We need to learn to talk to one another again. And we need to figure that out before the next pandemic hits.


This article was adapted from Anthony Fauci’s book On Call: A Doctor’s Journey in Public Service. It appears in the July/August 2024 print edition with the headline “The First Three Months.”

The only immovable object on my weekly calendar is a Sunday-night basketball game. We play in a rented gym in Washington, D.C., usually at a high school, because we’re all conserving cartilage and the local middle schools don’t place much cushioning underneath the hardwood. The game has been running for more than 20 years, but it wasn’t always on Sunday nights, and none of the original players is still around. When people get hurt or move away, they’re replaced like planks on the Ship of Theseus. The continuity of the game is the important thing. It has to stay in motion, but not because anyone is trying to get somewhere. None of our regulars retains any ambition of climbing up to some higher echelon of organized basketball, at least I hope not. That’s part of the game’s magic. The enlivening competitive energies that it summons have no higher purpose. They are entirely internal to the game. Play in earliest childhood has this quality.

In 2015, Nick Rogers, now a sociologist at the University of Pittsburgh, conducted an ethnography of a pickup-basketball game. Like an anthropologist who heads into the bush to live with tribe members, Rogers became one of the game’s regulars. During breaks, he took hurried notes on his iPhone. (Nice work, if you can get it.) Rogers wanted to understand the paradox of pickup basketball. Its culture is aggressively masculine. Its players tend to be diverse in age, race, and class. They jostle one another, elbow to elbow. They collide with full force. They get loud. And yet, fights are relatively rare. Rogers believes that this carefully pitched intensity is enabled by a special set of norms. These aren’t etched into stone like the Ten Commandments, he told me, but the players he interviewed on the sidelines were all fluent in them, and even reverent toward them. This unspoken code keeps the game from tipping over into violence. It allows a small group of perfect strangers with little in common besides basketball to experience a flow state—a brief, but intense, form of group transcendence.

Ethnographers like him have infiltrated nearly every part of the sports world. They have embedded themselves in locker rooms, team buses, and even vendor booths at baseball-card shows. One slipped into the cold Pacific along California’s coast on early mornings, for months, to study how surfers take turns. Pickup basketball has attracted particular attention from sociologists because it is such a social game. To play it well, five people—which is to say, a group roughly the size of a rock band, a hunting party, or a nuclear family—must move together in a way that can be improvised in real time. They may all be strangers, and yet the ball will pass among them as though controlled by one mind. I’ve been an intermittent part of these games for most of my adult life without ever really thinking through what they represent, or how they come together. One aspect of the paradox of pickup basketball is its invisibility to those who play.

[From April 2000: The best pickup-basketball player in America]

The sociologist Jason Jimerson conducted the first participant-observer study of pickup basketball, in the 1990s. He was inspired by a pair of writers who had traveled across the United States in search of the country’s best games. As a master’s student at the University of Virginia, Jimerson played every week at a gym near campus. He later published a paper describing how players maximized time on the court and quality of play. As a Ph.D. student at the University of Chicago, he returned to the subject for his dissertation. He began playing in a lunchtime game at the YMCA in Waukegan, a suburb just outside the city.

“Basketball started at the Y,” Jimerson told me. This one was right next to a courthouse. A judge and probation officer would sometimes play with someone who had recently been imprisoned. Between games, Jimerson dictated notes into a tape recorder. He even filmed some of the action. He wanted to compare different basketball cultures. He started playing at Cabrini-Green, a Chicago housing project that has since been torn down. When Jimerson’s colleagues told him that they feared for his safety, he sensed a touch of racism, but still, he took precautions. To endear himself to his fellow players, he bought a pair of expensive leather basketballs and brought them to games. “I knew there was a reason we let you study us,” one of them told him.

Jimerson has a poetic and plainspoken definition of sociology: He calls it “the science of people doing things together.” He took on pickup basketball as a research subject because it’s a very difficult thing that groups of people do together—even when they are very different from one another. If good feelings pass frequently among them, that helps. Rogers was interested in how players generate this atmosphere of fellow feeling. He had read Jimerson’s work; he was a prepared observer. He noticed that teammates maintained a strong norm of mutual encouragement, even—or especially—when one of them wasn’t very good. “Someone would miss a shot, and instead of their teammates saying, ‘Don’t shoot anymore, loser,’ they would say, ‘Keep shooting, shooter,’” Rogers told me. Players who dribbled endlessly, or attempted low-percentage fadeaway three-pointers, were also dealt with gently. Someone might communicate their displeasure by rolling their eyes, subtly, to other teammates or bystanders. But they wouldn’t confront those players directly.

To keep the larger game from breaking down, players also have to cooperate with their opponents, especially in the absence of neutral referees. The difficulty of this task depends on how many players are waiting on the sidelines, Jimerson told me. If there are just a few, then most people get to play again immediately whether they win or lose. As a consequence, they aren’t as competitive. The quality of the game diminishes, but there aren’t as many conflicts. The more players who are waiting, the higher the stakes, because losing may mean sitting through two games—and when stakes are too high, Jimerson said, “people really start fouling.”

The larger social order is most endangered during competitive games. Disputes may begin when players disagree about the score, or whether someone traveled or stepped out of bounds, but most happen when people argue about fouls. In pickup basketball, individual players must announce when they’ve been smacked, shoved, or otherwise touched inappropriately. Like any responsible sociologist, Jimerson is hesitant to traffic in universals, but he told me that nearly all pickup-basketball players have a norm against calling “ticky tack” fouls, which are too light to have really affected a person’s shot. The whole point of pickup basketball is to keep the game moving, he said. (Group flow states are a core interest for Jimerson; he has also done ethnographic research on musicians who perform in impromptu jam sessions.) This is why no one shoots free throws in pickup; it would interrupt the game. But so do extended arguments. In my Sunday-night game, we have an explicit norm that if a player says they were fouled, opposing players are supposed to respect the call, even if they disagree.

[Read: The science behind basketball’s biggest debate]

Such norms are standard in pickup basketball, but any player can tell you that they’re sometimes broken. Michael DeLand, a sociologist at Gonzaga University, told me that he observed extended disputes while playing in a long-running pickup game in Santa Monica. He chose it because it was more intimate than the world-famous games just down the coast at Venice Beach. He wanted to get to know the players. “There were Orthodox Jewish guys playing with businessmen, bartenders, bouncer types, rappers, and actors,” DeLand said. They arrived by foot, bike, bus, and car. Some became friends. DeLand noticed that when players engaged in extended arguments on the court, a folk legal process played out. People appealed to precedent. They made statements of evidence. Those who were waiting on the sidelines for the next game served as a jury, although their verdict wasn’t necessarily dispositive. Players on the blacktop would sometimes say, “Fuck you, you don’t get a say,” DeLand told me.

Rogers also studied disputes at the state-school gym where he played. He noticed upper limits to the intensity of verbal disagreement. Players were hesitant to use the sort of homophobic or misogynistic slurs that are common in, say, an online game of Call of Duty, because they would prolong the argument and make violence more likely. Even at their angriest, players would try to give off some signal that they weren’t taking the dispute so seriously, Rogers told me. They could be nose to nose, screaming at each other, but they would also smile subtly, or find another way to convey that they weren’t looking to escalate into a fight. In many instances, when players reached an impasse, someone would shoot to settle the matter. Rogers stressed that this was “more than just a semi-random way to resolve the dispute.” Players seemed to have a mystical belief that the basketball gods would dictate the outcome of the shot, expressed in an axiom familiar to almost all pickup-basketball players: “Ball don’t lie.”

Jimerson told me that he thinks of basketball as “a third place,” apart from home and work. In a third place, the usual social hierarchies are suppressed. People feel comfortable being themselves around strangers, and relating to others. That’s why a good regular game is a beautiful and fragile thing. I count myself lucky to have had a spot in one (or more) for nearly all of my adult life, and plan to keep it that way for as long as possible. I’ve known several guys who played into their 60s. It didn’t surprise me to learn that Jimerson is one of them. His last years on the court were some of his favorite. “Old guys have a different understanding of the game,” he told me. They know how to use back cuts and how to pass. They get into fewer disputes. They keep the game moving. The luckiest ones stay healthy long enough to play pickup with their adult kids.

Injuries give players a taste of dreaded, but inevitable, retirement. For the past few months, a friend I play with in a different game has been healing from a torn calf muscle. His doctor has barred him from the hardwood. He described this experience to me as a disturbance of the soul. Basketball is where he gets his exercise but also human connection. He shows up to the game with his full self, and he knows that others will too. “I love watching these grown-ass men limping around, giving every ounce of their energy to try to win,” he told me. On many holidays, he drops a message of gratitude into our WhatsApp group. He thanks us for the many blessings of the game and the microcommunity it has created. He talks about how much he cherishes it. Last week, he sent over a different message, an announcement. He described it as long overdue. He had been cleared to start stretching. By early July, he said, he’d be back on the court. It will be good to see him.

There’s no such thing as a miracle cure for weight loss, but the latest obesity drugs seem to come pretty close. People who take Ozempic or other weekly shots belonging to a class known as GLP-1 agonists, after the gut hormone they mimic, can lose a fifth or more of their body weight in a year. Incessant “food noise” fueling the urge to eat suddenly goes silent.

In recent months, the mystique of these drugs has only grown. Both semaglutide (sold under the brand names Ozempic and Wegovy) and tirzepatide (Mounjaro and Zepbound) were initially developed for diabetes and then repurposed for weight loss. But they apparently can do so much more than that. Studies showing the heart benefits of semaglutide have already led the FDA to approve Wegovy as a way to reduce the risk of major cardiac events, including stroke, heart attack, and death, in certain patients. The drug has also shown clear benefits for sleep apnea, kidney disease, liver disease—and can potentially help with fertility issues, Alzheimer’s, Parkinson’s, colorectal cancer, alcohol overuse, and even nail-biting. These days, a new use for GLP-1s seems to emerge every week.

With each new breakthrough, GLP-1s look more and more like the Swiss Army knife of medications. As Vox asked last year: “Is there anything Ozempic can’t do?” But GLP-1s can’t take all the credit. Obesity is linked to so many ailments that losing huge amounts of weight from these drugs is destined to have “a pretty dominant effect” on health outcomes, Randy Seeley, an obesity researcher at the University of Michigan, told me. Teasing out exactly what is causing these secondary benefits will be difficult. But the future of these drugs may hinge on it.

[Read: The future of obesity drugs just got way more real]

Some of the additional health effects of GLP-1s do seem in line with a drug that can lead to dramatic weight loss. People with obesity are at a much higher risk for heart attacks and liver disease; excessive weight can restrict breathing at night, leading to sleep apnea. Of course obesity drugs would help. Even reports of “Ozempic babies”—people unexpectedly conceiving while on GLP-1s—make sense considering that fertility tends to improve when people lose weight. But weight loss alone isn’t always the only explanation. A major trial tracking the heart health of people on semaglutide suggested that patients can have cardiovascular improvements even if they don’t lose much weight. “It is quite clear that there are benefits to these drugs that are beyond weight loss,” Seeley said.

GLP-1s improve health outcomes through three mechanisms, Daniel Drucker, a professor of medicine at the University of Toronto who co-discovered GLP-1 in the 1980s, told me. (Both Drucker and Seeley have consulted with GLP-1 manufacturers, as have many prominent obesity researchers.) The first mechanism involves the main functions of the drug: controlling blood sugar and inducing weight loss. That the drug coaxes the pancreas into secreting insulin led to its development for diabetes. Weight loss mostly happens through a separate process affecting the brain and gut that prompts a waning appetite and a lingering feeling of fullness. Disentangling their effects is difficult because high blood sugar can lead to weight gain, and is linked to many of the same chronic illnesses as obesity, including heart disease and cancer. The significant reductions in the risk of cardiovascular disease and death from chronic kidney disease seen by people on GLP-1 drugs “certainly reflect” both changes in blood sugar and weight, Drucker said.

A second mechanism that could explain some of these health effects is that the drugs act directly on certain organs. GLP-1 receptors exist on tissues all over the body: throughout the lungs, kidneys, cardiovascular system, gut, skin, and central nervous system. The drugs’ heart benefits, for example, might involve GLP-1 receptors in the heart and blood vessels, Steven Heymsfield, a professor who studies obesity at Louisiana State University, told me.

Beyond affecting individual organs, GLP-1s likely spur wide-ranging effects across the body through a third, more generalized process: reducing inflammation. Chronic diseases associated with obesity and diabetes, such as liver, kidney, and cardiovascular disease, are “all driven in part by increased inflammation,” which GLP-1s can help reduce, Drucker said.

In some situations, these mechanisms may work hand in hand, as in the case of Alzheimer’s. An older GLP-1 drug called liraglutide has shown potential as a treatment for Alzheimer’s, and semaglutide’s effect on early stages of the disease is being tested in a Phase 3 trial. The brain is littered with GLP-1 receptors, inflammation is known to be a central driver of neurodegeneration, and losing weight and having lower blood sugar “will probably help reduce the rate of cognitive decline,” Drucker said.

More complex effects will be harder to disentangle. The drugs are thought to curb addictive and compulsive behaviors, such as alcohol overuse, impulse shopping, and gambling. In animals, GLP-1s have been shown to affect the brain’s reward circuitry—a handy explanation, but perhaps an overly simplistic one. “Reward isn’t just one thing,” Seeley said. The mechanism that makes eating rewarding may differ slightly from that of smoking or gambling. If that’s the case, it wouldn’t make sense for a single drug to tamp down all of those behaviors.

[Read: Did scientists accidentally invent an anti-addiction drug?]

Still other benefits of GLP-1s have yet to be explained. In a large study of people with diabetes published in February, those who took GLP-1s had a lower risk of colorectal cancer than those who didn’t—and weight didn’t seem to be a factor. One possible explanation for the link is that the drugs reduce inflammation that could lead to cancer. Yet recent research in mice suggests that blocking the GLP-1 receptor—that is, doing the opposite of what the drugs do—is what triggers the immune system to fight colorectal cancer.

Some of the ancillary effects being observed now will prove to be legitimate; others won’t. “This happens every time we discover a new molecule,” Seeley said. At first, a drug proves to be amazingly effective against the condition it’s designed to treat. As more people use it, new effects come to light; before long, it begins to seem like a cure-all. Research ensues. Then, the comedown: The studies, when completed, show that it can treat some conditions but not others. In the 1980s, statins emerged as a powerful treatment for high cholesterol, and excitement then mounted about their additional benefits on kidney disease and cognitive decline. Now statins are largely used for their original purpose.

Each new discovery about what GLP-1s can do seems like a lucky surprise—a bonus effect of already miraculous drugs. But people don’t want drugs that are surprising. They want ones that are effective: not medications that might lower their risk of other illnesses, but those that will. To make those drugs, manufacturers need to know what’s actually happening in the body—to what degree the health effects can be attributed to more than just weight loss. To prescribe those drugs, health-care providers need to know the same thing. Doing so will become even harder as GLP-1s themselves become more complicated, targeting multiple other metabolic pathways, each with their own downstream effects. Tirzepatide already targets an additional hormone on top of GLP-1, and a drug that targets three hormones is on its way.

A fuller picture of the potential of GLP-1s may begin to emerge soon. Some of the trials investigating their effects on early Alzheimer’s and Parkinson’s are expected to have results before the end of 2025, offering “a glimpse of whether or not they work,” Drucker said. Eventually, studies may reveal how they work—for these and all the other ancillary benefits. Drug companies are in a furious battle to develop new kinds of obesity drugs, and as it’s shaping up, the future of these medications may not entirely be about obesity. As new kinds of drugs are developed, drugmakers will have to consider whether they maintain, improve upon, or weaken the other benefits, according to Drucker. Competition will likely give rise to a wide range of drugs, each specific to a certain condition or combination of them. GLP-1s might follow the trajectory of blood-pressure medications, which come in more than 200 types to suit all kinds of patients.

New benefits will propel GLP-1 further into the mainstream—not just by opening them up to new subsets of people, but by adding pressure on insurance providers to cover them. Medicare doesn’t pay for obesity drugs, in part because the federal government has historically considered weight loss to be a cosmetic issue, not a medical one. But in March, after the FDA extended Wegovy’s approval to include reducing cardiovascular risk in people with obesity, some Medicare plans began to offer coverage to patients with both weight and heart problems. That GLP-1s have multiple uses is not in itself miraculous. But it would be a small miracle if all of their additional effects, whether separate from or downstream of weight loss, are what help obesity drugs become as widely available as so many other life-changing treatments.

Updated at 12:05 p.m. ET on June 7, 2024

Our most recent flu pandemic—2009’s H1N1 “swine flu”—was, in absolute terms, a public-health crisis. By scientists’ best estimates, roughly 200,000 to 300,000 people around the world died; countless more fell sick. Kids, younger adults, and pregnant people were hit especially hard.

That said, it could have been far worse. Of the known flu pandemics, 2009’s took the fewest lives; during the H1N1 pandemic that preceded it, which began in 1918, a flu virus infected an estimated 500 million people worldwide, at least 50 million of whom died. Even some recent seasonal flus have killed more people than swine flu did. With swine flu, “we got lucky,” Seema Lakdawala, a virologist at Emory University, told me. H5N1 avian flu, which has been transmitting wildly among animals, has not yet spread in earnest among humans. Should that change, though, the world’s next flu pandemic might not afford us the same break.

[Read: Cows have almost certainly infected more than two people with bird flu]

Swine flu caught scientists by surprise. At the time, many researchers were dead certain that an H5N1, erupting out of somewhere in Asia, would be the next Big Bad Flu. Their focus was on birds; hardly anyone was watching the pigs. But the virus, a descendant of the devastating flu strain that caused the 1918 pandemic, found its way into swine and rapidly gained the ability to hack into human airway cells. It was also great at traveling airborne—features that made it well positioned to wreak global havoc, Lakdawala said. By the time experts caught on to swine flu’s true threat, “we were already seeing a ton of human cases,” Nahid Bhadelia, the founding director of the Boston University Center on Emerging Infectious Diseases, told me. Researchers had to scramble to catch up. But testing was intermittent, and reporting of cases was inconsistent, making it difficult for scientists to get a handle on the virus’s spread. Months passed before the rollout of a new vaccine began, and uptake was meager. Even in well-resourced countries such as the U.S., few protections hindered the virus’s initial onslaught.

But the worst never came to pass—for reasons that experts still don’t understand. Certainly, compared with the 1918 pandemic, or even those in the 1950s and ’60s, modern medicine was better equipped to test for and treat flu; although vaccine uptake has never been perfect, the availability of any shots increased protection overall, Sam Scarpino, an infectious-disease modeler and the director of AI and life sciences at Northeastern University, told me. Subtler effects may have played a role too. Other H1N1 viruses had been circulating globally since the late 1970s, potentially affording much of the population a degree of immunity, Troy Sutton, a virologist at Pennsylvania State University, told me. Older people, especially, may have harbored an extra dose of defense, from additional exposure to H1N1 strains from the first half of the 20th century. (After the 1918 pandemic, versions of that virus stuck around, and continued to percolate through the population for decades.) Those bonus safeguards might help explain why younger people were so severely affected in 2009, Lakdawala told me.

Some of those same factors could end up playing a role in an H5N1 epidemic. But 2009 represents an imperfect template—especially when so much about this new avian flu remains unclear. True human-to-human spread of H5N1 is still a distant possibility: For that, the virus would almost certainly need to undergo some major evolutionary alterations to its genome, potentially even transforming into something almost unrecognizable. All of this muddies any predictions about how a future outbreak might unfold.

Still, experts are keeping a close eye on a few factors that could raise H5N1’s risks. For instance, no versions of H5N1 flu have ever gained a sustained foothold in people, which means “there’s very little immunity in the community,” Michael Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told me.

Exposure to other flu strains could offer limited protection. Lakdawala and Sutton have been running experiments in ferrets, which transmit and fall ill with flu much like people do. Their preliminary results suggest that animals with previous exposures to seasonal-flu strains experience milder disease when they’re next hit with this particular H5N1. That said, ferrets with zero prior flu experience—which would be the case for some very young kids—fare poorly, worse than they do with the H1N1 of 2009, and “that’s scary,” Lakdawala told me.

It’s too early to say how those results would translate into people, for whom data are sparse. Since this H5N1 virus was first detected in the 1990s, scientists have recorded hundreds of human cases, nearly half of whom have died. (Avian flus that spill intermittently people often have this kind of nasty track record: This week, the WHO reported that another kind of bird flu, designated H5N2, killed a man in Mexico in late April. It was the flu subtype’s first recorded instance in a human; no evidence suggests yet that this virus has the ability to spread among people, either.) Experts caution strongly against reading too much into the stats: No one can be certain how many people the virus has actually infected, making it impossible to estimate a true fatality rate. The virus has also shape-shifted over decades—and the versions of it that killed those people did not seem capable of spreading among them. As Sutton pointed out, past experiments suggest that the mutations that could make H5 viruses more transmissible might also make them a bit less deadly. That’s not a guarantee, however: The 1918 flu, for instance, “transmitted really well in humans and caused very severe disease,” Sutton said.

[Read: America’s infectious-disease barometer is off]

Scientists also can’t extrapolate much from the fact that recent H5N1 infections among dairy workers in the U.S. have been documented as mild. Many people who work on farms are relatively young and healthy, Bhadelia noted; plus, their exposures have, presumably, been through virus-laden raw milk. The virus could affect a different community in more dramatic ways, and the nature of the disease could shift if the virus entered the body via another route. And “mildness” in the short term isn’t always a comfort, Scarpino said: As with COVID, the disease could still have chronic consequences for someone’s health.

The world is in some ways better prepared for H5N1 than it was in 2009. Scientists have had eyes on this particular avian flu for decades; in the past few years alone, they’ve watched it hopscotch into dozens of animal species, and tracked the genetic tweaks it’s made. Already, U.S. experts are testing for the pathogen in wastewater, and federal regulators have taken action to halt its spread in poultry and livestock. H5 vaccines are stockpiled, and more are on the way—a pipeline that may be speedier than ever before, thanks to the recent addition of mRNA tech.

[Read: The bird-flu host we should worry about]

But this close to the worst days of the COVID-19 pandemic, Osterholm and others worry that halting any outbreak will be harder than it otherwise would have been. “We could see many, many individuals refusing to get a vaccine,” he said. (That may be especially true if two doses are required for protection.) Bhadelia echoed that concern, adding that she’s already seeing a deluge of misinformation on social media. And Scarpino noted that, after the raging debates over COVID-era school closures, legislators may refuse to entertain the option again—even though children are some of the best conduits for flu viruses. Stopping a pandemic requires trust, coordination, and public buy-in. On that front alone, Osterholm said, “without a doubt, I think we’re less prepared.”

The world has a track record of not taking flu seriously—even, sometimes, when it sparks a pandemic. In the months following the initial outbreaks of swine flu, the outbreak was mocked as a nothingburger; public-health officials were criticized for crying wolf. But the arguably “mild” flu epidemic still filled hospital emergency departments with pneumonia cases, spreading the virus to scores of health-care workers; kids still fell sick in droves. So many young people died that, in terms of years of life lost, Osterholm told me, the toll of 2009 still exceeded those of the flu pandemics that began in 1957 and 1968. Nor are comparisons with seasonal flus exactly a comfort: Most years, those epidemics kill tens of thousands of people in the U.S. alone.

H5N1 could also permanently alter the world’s annual flu burden. An avian-flu pandemic could present the perfect opportunity for this virus to join the other flus that transmit seasonally—becoming endemic threats that may be with us for good. “We’ve seen that with every flu pandemic that’s occurred,” Sutton told me. More circulating flu viruses could mean more flu cases each year—or, perhaps, more chances for these viruses to mingle their genetic material and generate new versions of themselves to which the population lacks immunity.

However likely those possibilities are, halting H5N1’s spread now would preclude all of them. Scientists have foresight on this avian flu in a way they never did with pre-pandemic swine flu. Capitalizing on that difference—perhaps the most important one between these two flus—could keep us from experiencing another outbreak at all.

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