Katherine J. Wu

When Kathleen Walker-Meikle, a historian at the University of Basel, in Switzerland, ponders the Middle Ages, her mind tends to drift not to religious conquest or Viking raids, but to squirrels. Tawny-backed, white-bellied, tufted-eared red squirrels, to be exact. For hundreds of years, society’s elites stitched red-squirrel pelts into luxurious floor-length capes and made the animals pets, cradling them in their lap and commissioning gold collars festooned with pearls.

The ongoing outbreak of H5N1 avian flu virus looks a lot like a public-health problem that the United States should be well prepared for.
Although this version of flu is relatively new to the world, scientists have been tracking H5N1 for almost 30 years. Researchers know the basics of how flu spreads and who tends to be most at risk. They have experience with other flus that have jumped into us from animals. The U.S.

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Within the next couple of decades, a new generation of contraceptives could hit the American market. One, a pill that blocks certain cells from accessing vitamin A, might be able to limit fertility without flooding the body with hormones; another is an injection that temporarily blocks up the reproductive plumbing.

Updated at 6:50 p.m. ET on March 15, 2024
At about 3:30 a.m., four hours into our drive, Travis Livieri’s phone began to thrum. “I’ve got a ferret for you,” a voice crackled through the static. The animal in question was one of North America’s most endangered mammals, for which the next hour might be the strangest of her life; for Livieri, the wildlife biologist tasked with saving her, it would be one of thousands of interventions he’s made to prevent her kind from permanently vanishing.

Four years after what was once the “novel coronavirus” was declared a pandemic, COVID remains the most dangerous infectious respiratory illness regularly circulating in the U.S. But a glance at the United States’ most prominent COVID policies can give the impression that the disease is just another seasonal flu.

In the late aughts, while working on the island of Jersey, in the United Kingdom, Erica Cartmill found herself staring at a daughter giving her mother some grief.
The little one was waving a stick in her mother’s face and then yanking it back when her mother reached to snatch the object away—a performance so persistent, so targeted, Cartmill told me, that it was almost impossible for the grown-up to ignore.

In Arnold Monto’s ideal vision of this fall, the United States’ flu vaccines would be slated for some serious change—booting a major ingredient that they’ve consistently included since 2013. The component isn’t dangerous. And it made sense to use before. But to include it again now, Monto, an epidemiologist and a flu expert at the University of Michigan, told me, would mean vaccinating people “against something that doesn’t exist.

Out on the savannas of East Africa, lions have always loomed large. Clocking in at several hundred pounds apiece and capable of ending a zebra’s life in a single swift bite, they’re veritable food-web royalty.
But in certain parts of their habitat, these hefty carnivores are now under threat from an unlikely and petite new nemesis: an invasive ant, puny enough to fit inside a hollowed-out sesame seed. The two creatures rarely, if ever, directly interact.

Across the Northeast, forests are haunted by the ghosts of American giants. A little more than a century ago, these woods brimmed with American chestnuts—stately Goliaths that could grow as high as 130 feet tall and more than 10 feet wide. Nicknamed “the redwoods of the East,” some 4 billion American chestnuts dotted the United States’ eastern flank, stretching from the misty coasts of Maine down into the thick humidity of Appalachia.

Earlier this month, Taison Bell walked into the intensive-care unit at UVA Health and discovered that half of the patients under his care could no longer breathe on their own. All of them had been put on ventilators or high-flow oxygen.

In Linfa Wang’s ideal world, all humans would be just a bit more bat-like.Wang, a biochemist and zoonotic-disease expert at Duke-NUS Medical School, in Singapore, has no illusions about people flapping about the skies or echolocating to find the best burger in town. The point is “not to live like a bat,” Wang told me, but to take inspiration from their very weird physiology in order to boost the quality, or even the length, of human life.

In the early 1990s, while studying preeclampsia in Guadeloupe, Pierre-Yves Robillard hit upon a realization that seemed to shake the foundations of his field. Preeclampsia, a pregnancy complication that causes some 500,000 fetal deaths and 70,000 maternal deaths around the world each year, had for decades been regarded as a condition most common among new mothers, whose bodies were mounting an inappropriate attack on a first baby.

As the chair of the department of obstetrics and gynecology at UT Southwestern Medicine, Catherine Spong is used to seeing a lot of baby bumps. But through her decades of practice, she’s been fascinated by a different kind of bump: Year after year after year, she and her colleagues deliver a deluge of babies from June through September, as much as a 10 percent increase in monthly rates over what they see from February through April. “We call it the summer surge,” Spong told me.

Paul Offit is not an anti-vaxxer. His résumé alone would tell you that: A pediatrician at Children’s Hospital of Philadelphia, he is the co-inventor of a rotavirus vaccine for infants that has been credited with saving “hundreds of lives every day”; he is the author of roughly a dozen books on immunization that repeatedly debunk anti-vaccine claims. And from the earliest days of COVID-19 vaccines, he’s stressed the importance of getting the shots.

Back in the spring, around the end of the COVID-19 public-health emergency, hospitals around the country underwent a change in dress code. The masks that staff had been wearing at work for more than three years vanished, in some places overnight.

This article was featured in One Story to Read Today, a newsletter in which our editors recommend a single must-read from The Atlantic, Monday through Friday. Sign up for it here.For years, the American approach to protein has been a never-ending quest for more. On average, each person in the United States puts away roughly 300 pounds of meat a year; we are responsible for more than a third of the multibillion-dollar protein-supplement market.

Anoles have always been happy in the heat. The svelte little lizards, a group some 400 species strong, thrive in the Americas’ warmest parts—from the balmy rainforests of South America up through the United States’ Sun Belt—where they spend their days basking on boulders and scurrying out to the sun-soaked tips of twigs, or even scampering over the blistering metal of exposed city pipes.

For more than a year, life for many sriracha lovers has been an excruciating lesson in bland. Shortages of red jalapeños—the key ingredient in the famous hot sauce—have gotten bleak, in particular for the ultra-popular version of the condiment made by Huy Fong Foods. Grocery stores have enforced buying limits on customers. Bottles on eBay, Craigslist, and Amazon are selling for eye-watering prices—as much as $50 or more.

As recently as the 1990s, Jodi Stookey, a nutrition consultant based in California, remembers hydration research being a very lonely field. The health chatter was all about fat and carbs; children routinely subsisted on a single pouch of Capri Sun a day. Even athletes were discouraged from sipping on fields and race tracks, lest the excess liquid slow them down.

Since the pandemic’s earliest days, epidemiologists have been waiting for the coronavirus to finally snap out of its pan-season spree. No more spring waves like the first to hit the United States in 2020, no more mid-year surges like the one that turned Hot Vax Summer on its head. Eventually, or so the hope went, SARS-CoV-2 would adhere to the same calendar that many other airway pathogens stick to, at least in temperate parts of the globe: a heavy winter peak, then a summer on sabbatical.

In the three-plus decades I’ve been alive, I have never been bitten by a tick. Actually, that may be a lie, and I have no way of knowing for sure. Because even though ticks have harpoonlike mouthparts, even though certain species can latch on for up to two weeks, even though some guzzle enough blood to swell 100 times in weight, their bites are disturbingly discreet.

Late last night, New Yorkers were served a public-health recommendation with a huge helping of déjà vu: “If you are an older adult or have heart or breathing problems and need to be outside,” city officials said in a statement, “wear a high-quality mask (e.g. N95 or KN95).”It was, in one sense, very familiar advice—and also very much not. This time, the threat isn’t viral, or infectious at all.

In March 2020, Yamagata’s trail went cold.The pathogen, one of the four main groups of flu viruses targeted by seasonal vaccines, had spent the first part of the year flitting across the Northern Hemisphere, as it typically did. As the seasons turned, scientists were preparing, as they typically did, for the virus to make its annual trek across the equator and seed new outbreaks in the globe’s southern half.That migration never came to pass.

Updated at 2:45 p.m. on March 21, 2023
Last week, the ongoing debate about COVID-19’s origins acquired a new plot twist. A French evolutionary biologist stumbled across a trove of genetic sequences extracted from swabs collected from surfaces at a wet market in Wuhan, China, shortly after the pandemic began; she and an international team of colleagues downloaded the data in hopes of understanding who—or what—might have ferried the virus into the venue.

Updated at 1:40 a.m. ET on March 17, 2023For three years now, the debate over the origins of the coronavirus pandemic has ping-ponged between two big ideas: that SARS-CoV-2 spilled into human populations directly from a wild-animal source, and that the pathogen leaked from a lab.

In the spring of 1986, in their rush to flee the radioactive plume and booming fire that burned after the Chernobyl power plant exploded, many people left behind their dogs. Most of those former pets died as radiation ripped through the region and emergency workers culled the animals they feared would ferry toxic atoms about. Some, though, survived. Those dogs trekked into the camps of liquidators to beg for scraps; they nosed into empty buildings and found safe places to sleep.

In the early days of the pandemic, one of the scariest and most surprising features of SARS-CoV-2 was its stealth. Initially assumed to transmit only from people who were actively sick—as its predecessor SARS-CoV did—the new coronavirus turned out to be a silent spreader, also spewing from the airways of people who were feeling just fine.

For the past few weeks, my daily existence has been scored by the melodies of late winter: the drip of melting ice, the soft rustling of freshly sprouted leaves—and, of course, the nonstop racket of sneezes and coughs.The lobby of my apartment building is alive with the sounds of sniffles and throats being cleared. Every time I walk down the street, I’m treated to the sight of watery eyes and red noses.

In one very specific and mostly benign way, it’s starting to feel a lot like the spring of 2020: Disinfection is back.“Bleach is my friend right now,” says Annette Cameron, a pediatrician at Yale School of Medicine, who spent the first half of this week spraying and sloshing the potent chemical all over her home. It’s one of the few tools she has to combat norovirus, the nasty gut pathogen that her 15-year-old son was recently shedding in gobs.

Eleven years ago, on the remote Japanese island of Kojima, a female macaque walked backwards into a stray heap of primate poop, glanced down at her foot, and completely flipped her lid.