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  • The Other Group of Viruses That Could Cause the Next Pandemic

    The Other Group of Viruses That Could Cause the Next Pandemic

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    Whether it begins next week, next year, or next decade, another pandemic is on its way. Researchers can’t predict precisely when or how the outbreak might begin. Some 1.6 million viruses are estimated to lurk in the world’s mammalian and avian wildlife, up to half of which could spill into humans; an untold number are attempting exactly that, at this very moment, bumping up against the people hunting, eating, and encroaching on those creatures. (And that’s just viruses: Parasites, fungi, and bacteria represent major infectious dangers too.) The only true certainty in the pandemic forecast is that the next threat will be here sooner than anyone would like.

    But scientists can at least make an educated guess about what might catalyze the next Big One. Three main families of viruses, more than most others, keep scientists up at night: flu viruses, coronaviruses, and paramyxoviruses, in descending order of threat. Together, those groups make up “the trifecta of respiratory death,” Sara Cherry, a virologist at the University of Pennsylvania, told me.

    Flu and coronavirus have a recent track record of trouble: Since 1918, flu viruses have sparked four pandemics, all the while continuing to pester us on a seasonal basis; some scientists worry that another major human outbreak may be brewing now, as multiple H5 flu viruses continue to spread from birds to mammals. The past two decades have also featured three major and deadly coronavirus outbreaks: the original SARS epidemic that began in late 2002; MERS, which spilled into humans—likely from camels—in 2012; and SARS-CoV-2, the pandemic pathogen that’s been plaguing us since the end of 2019. Common-cold-causing coronaviruses, too, remain a fixture of daily living—likely relics of ancient animal-to-human spillovers that we kept transmitting amongst ourselves.

    Read: Bird flu has never done this before

    Paramyxoviruses, meanwhile, have mostly been “simmering in the background,” says Raina Plowright, a disease ecologist at Cornell. Unlike flu viruses and coronaviruses, which have already clearly “proven themselves” as tier-one outbreak risks, paramyxoviruses haven’t yet been caught causing a bona fide pandemic. But they seem poised to do so, and they likely have managed the feat in the past. Like flu viruses and coronaviruses, paramyxoviruses can spread through the air, sometimes very rapidly. That’s certainly been the case with measles, a paramyxovirus that is “literally the most transmissible human virus on the planet,” says Paul Duprex, a virologist at the University of Pittsburgh. And, like flu viruses and coronaviruses, paramyxoviruses are found in a wide range of animals; more are being discovered wherever researchers look. Consider canine distemper virus, which has been found in, yes, canines, but also in raccoons, skunks, ferrets, otters, badgers, tigers, and seals. Paramyxoviruses, like flu viruses and coronaviruses, have also repeatedly shown their potential to hopscotch from those wild creatures into us. Since 1994, Hendra virus has caused multiple highly lethal outbreaks in horses, killing four humans along the way; the closely related Nipah virus has, since 1998, spread repeatedly among both pigs and people, carrying fatality rates that can soar upwards of 50 percent.

    The human versions of those past few outbreaks have petered out. But that may not always be the case—for Nipah, or for another paramyxovirus that’s yet to emerge. It’s entirely possible, Plowright told me, that the world may soon encounter a new paramyxovirus that’s both highly transmissible and ultra deadly—an “absolutely catastrophic” scenario, she said, that could dwarf the death toll of any epidemic in recent memory. (In the past four years, COVID-19, a disease with a fatality rate well below Nipah’s, has killed an estimated 7 million people.)

    All that said, though, paramyxoviruses are a third-place contender for several good reasons. Whereas flu viruses and coronaviruses are speedy shape-shifters—they frequently tweak their own genomes and exchange genetic material with others of their own kind—paramyxoviruses have historically been a bit more reluctant to change. “That takes them down a level,” says Danielle Anderson, a virologist at the Doherty Institute, in Melbourne. For one, these viruses’ sluggishness could make it much tougher for them to acquire transmission-boosting traits or adapt rapidly to spread among new hosts. Nipah virus, for instance, can spread among people via respiratory droplets at close contact. But even though it’s had many chances to do so, “it still hasn’t gotten very good at transmitting among humans,” Patricia Thibault, a biologist at the University of Saskatchewan who studied paramyxoviruses for years, told me.

    The genetic stability of paramyxoviruses can also make them straightforward to vaccinate against. Our flu and coronavirus shots need regular updates—as often as annually—to keep our immune system apace with viral evolution. But we’ve been using essentially the same measles vaccine for more than half a century, Duprex told me, and immunity to the virus seems to last for decades. Strong, durable vaccines are one of the main reasons that several countries have managed to eliminate measles—and why a paramyxovirus called rinderpest, once a major scourge of cattle, is one of the only infectious diseases we’ve ever managed to eradicate. In both cases, it helped that the paramyxovirus at play wasn’t great at infecting a ton of different animals: Measles is almost exclusive to us; rinderpest primarily troubled cows and their close kin. Most flu viruses and SARS-CoV-2, meanwhile, can spread widely across the tree of animal life; “I don’t know how you can eradicate that,” Anderson told me.

    The problem with all of these trends, though, is that they represent only what researchers know of the paramyxoviruses they’ve studied—which is, inevitably, a paltry subset of what exists, says Benhur Lee, a virologist at Mount Sinai’s Icahn School of Medicine. “The devil we don’t know can be just as frightening,” if not more, Lee told me. A pattern-defying paramyxovirus may already be readying itself to jump.

    Researchers are keyed into these looming threats. The World Health Organization highlights Nipah virus and its close cousins as some of its top-priority pathogens; in the U.S., paramyxoviruses recently made a National Institute of Allergy and Infectious Diseases list of pathogens essential to study for pandemic preparedness. Last year, the Bill & Melinda Gates Foundation announced a hefty initiative to fund paramyxovirus antiviral drugs. Several new paramyxovirus vaccines—many of them targeting Nipah viruses and their close relatives—may soon be ready to debut.

    Read: We have a mink problem

    At the same time, though, paramyxoviruses remain neglected—at least relative to the sheer perils they pose, experts told me. “Influenza has been sequenced to death,” Lee said. (That’s now pretty true for SARS-CoV-2 as well.) Paramyxoviruses, meanwhile, aren’t regularly surveilled for; development of their treatments and vaccines also commands less attention, especially outside of Nipah and its kin. And although the family has been plaguing us for countless generations, researchers still don’t know exactly how paramyxoviruses move into new species, or what mutations they would need to become more transmissible among us; they don’t know why some paramyxoviruses spark only minor respiratory infections, whereas others run amok through the body until the host is dead.

    Even the paramyxoviruses that feel somewhat familiar are still surprising us. In recent years, scientists have begun to realize that immunity to the paramyxovirus mumps, once thought to be pretty long-lasting and robust, wanes in the first few decades after vaccination; a version of the virus, once thought to be a problem only for humans and a few other primates, has also been detected in bats. For these and other reasons, rubulaviruses—the paramyxovirus subfamily that includes mumps—are among the potential pandemic agents that most concern Duprex. Emmie de Wit, the chief of the molecular-pathogenesis unit at Rocky Mountain Laboratories, told me that the world could also become more vulnerable to morbilliviruses, the subfamily that includes measles. If measles is ever eradicated, some regulators may push for an end to measles shots. But in the same way that the end of smallpox vaccination left the world vulnerable to mpox, the fall of measles immunity could leave an opening for a close cousin to rise.

    The next pandemic won’t necessarily be a paramyxovirus, or even a flu virus or a coronavirus. But it has an excellent chance of starting as so many other known pandemics have—with a spillover from animals, in parts of the world where we’ve invaded wild habitats. We may not be able to predict which pathogen or creature might be involved in our next big outbreak, but the common denominator will always be us.

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    Katherine J. Wu

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  • The Big COVID Question for Hospitals This Fall

    The Big COVID Question for Hospitals This Fall

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    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. At UChicago Medicine, where masking policies softened at the end of May, Emily Landon, the executive medical director of infection prevention and control, fielded hate mail from colleagues, some chiding her for waiting too long to lift the requirement, others accusing her of imperiling the immunocompromised. At Vanderbilt University Medical Center, which did away with masking in April, ahead of many institutions, Tom Talbot, the chief hospital epidemiologist, was inundated with thank-yous. “People were ready; they were tired,” he told me. “They’d been asking for several months before that, ‘Can we not stop?’”

    But across hospitals and policies, infection-prevention experts shared one sentiment: They felt almost certain that the masks would need to return, likely by the end of the calendar year. The big question was exactly when.

    For some hospitals, the answer is now. In recent weeks, as COVID-19 hospitalizations have been rising nationwide, stricter masking requirements have returned to a smattering of hospitals in Massachusetts, California, and New York. But what’s happening around the country is hardly uniform. The coming respiratory-virus season will be the country’s first after the end of the public-health emergency—its first, since the arrival of COVID, without crisis-caliber funding set aside, routine tracking of community spread, and health-care precautions already in place. After years of fighting COVID in concert, hospitals are back to going it alone.

    A return to masking has a clear logic in hospitals. Sick patients come into close contact; medical procedures produce aerosols. “It’s a perfect storm for potential transmission of microbes,” Costi David Sifri, the director of hospital epidemiology at UVA Health, told me. Hospitals are on the front lines of disease response: They, more than nearly any other place, must prioritize protecting society’s vulnerable. And with one more deadly respiratory virus now in winter’s repertoire, precautions should logically increase in lockstep. But “there is no clear answer on how to do this right,” says Cameron Wolfe, an infectious-disease physician at Duke. Americans have already staked out their stances on masks, and now hospitals have to operate within those confines.

    When hospitals moved away from masking this spring, they each did so at their own pace—and settled on very different baselines. Like many other hospitals in Massachusetts, Brigham and Women’s Hospital dropped its mask mandate on May 12, the day the public-health emergency expired; “it was a noticeable difference, just walking around the hospital” that day, Meghan Baker, a hospital epidemiologist for both Brigham and Women’s Hospital and Dana-Farber Cancer Institute, told me. UVA Health, meanwhile, weaned staff off of universal masking over the course of about 10 weeks.

    Most masks at the Brigham are now donned on only a case-by-case basis: when a patient has active respiratory symptoms, say, or when a health-care worker has been recently sick or exposed to the coronavirus. Staff also still mask around the same subset of vulnerable patients that received extra protection before the pandemic, including bone-marrow-transplant patients and others who are highly immunocompromised, says Chanu Rhee, an associate hospital epidemiologist at Brigham and Women’s Hospital. UVA Health, meanwhile, is requiring masks for everyone in the hospital’s highest-risk areas—among them, certain intensive-care units, as well as cancer, transplant, and infusion wards. And although Brigham patients can always request that their providers mask, at UVA, all patients are asked upon admission whether they’d like hospital staff to mask.

    Nearly every expert I spoke with told me they expected that masks would at some point come back. But unlike the early days of the pandemic, “there is basically no guidance from the top now,” Saskia Popescu, an epidemiologist and infection-prevention expert at the University of Maryland School of Medicine, said. The CDC still has a webpage with advice on when to mask. Those recommendations are tailored to the general public, though—and don’t advise covering up until COVID hospital admissions go “way high, when the horse has well and truly left the barn,” Landon, at UChicago, told me. “In health care, we need to do something before that”—tamping down transmission prior to wards filling up.

    More specific advice could still emerge from the CDC, or individual state health departments. But going forward, the assumption is that “each hospital is supposed to have its own general plan,” Rhee told me. (I reached out to the CDC repeatedly about whether it might update its infection-prevention-guidance webpage for COVID—last retooled in May—but didn’t receive a response.)

    Which leaves hospitals with one of two possible paths. They could schedule a start to masking season, based on when they estimate cases might rise—or they could react to data as they come in, tying masking policies to transmission bumps. With SARS-CoV-2 still so unpredictable, many hospitals are opting for the latter. That also means defining a true case rise—“what I think everybody is struggling with right now,” Rhee said. There is no universal definition, still, for what constitutes a surge. And with more immunity layered over the population, fewer infections are resulting in severe disease and death—even, to a limited extent, long COVID—making numbers that might have triggered mitigations just a year or two ago now less urgent catalysts.

    Read: The future of long COVID

    Further clouding the forecast is the fact that much of the data that experts once relied on to monitor COVID in the community have faded away. In most parts of the country, COVID cases are no longer regularly tallied; people are either not testing, or testing only at home. Wastewater surveillance and systems that track all influenza-like illnesses could provide some support. But that’s not a whole lot to go on, especially in parts of the country such as Tennessee, where sewage isn’t as closely tracked, Tom Talbot, of Vanderbilt, told me.

    Some hospitals have turned instead to in-house stats. At Duke—which has adopted a mitigation policy that’s very similar to UVA’s—Wolfe has mulled pulling the more-masking lever when respiratory viruses account for 2 to 4 percent of emergency and urgent-care visits; at UVA, Sifri has considered taking action once 1 or 2 percent of employees call out sick, with the aim of staunching sickness and preserving staff. “It really doesn’t take much to have an impact on our ability to maintain operations,” Sifri told me. But “I don’t know if those are the right numbers.” Plus, internal metrics are now tricky for the same reasons they’ve gotten shaky elsewhere, says Xiaoyan Song, the chief infection-control officer at Children’s National Hospital, in Washington, D.C. Screening is no longer routine for patients, skewing positivity stats; even sniffly health-care workers, several experts told me, are now less eager to test and report.

    Read: What COVID hospitalization numbers are missing

    For hospitals that have maintained a more masky baseline, scenarios in which universal masking returns are a little easier to envision and enact. At UChicago Medicine, Landon and her colleagues have developed a color-coded system that begins at teal—masking for high-risk patients, patients who request masked care, and anyone with symptoms, plus masking in high-risk areas—and goes through everyone-mask-up-everywhere red; their team plans to meet weekly to assess the situation, based on a variety of community and internal metrics, and march their masking up or down. Wolfe, of Duke, told me that his hospital “wanted to reserve a little bit of extra masking quite intentionally,” so that any shift back toward stricter standards would feel like less of a shock: Habits are hard to break and then reform.

    Other hospitals that have been living mostly maskless for months, though, have a longer road back to universal masking, and staff members who might not be game for the trek. Should masks need to return at the Brigham or Dana-Farber, for instance, “I suspect the reaction will be mixed,” Baker told me. “So we really are trying to be judicious.” The hospital might try to preserve some maskless zones in offices and waiting rooms, for instance, or lower-risk rooms. And at Children’s National, which has also largely done away with masks, Song plans to follow the local health department’s lead. “Once D.C. Health requires hospitals to reimplement the universal-masking policy,” she told me, “we will be implementing it too.”

    Other mitigations are on the table. Several hospital epidemiologists told me they expected to reimplement some degree of asymptomatic screening for various viruses around the same time they reinstate masks. But measures such as visiting restrictions are a tougher call. Wolfe is reluctant to pull that lever before he absolutely has to: Going through a hospital stay alone is one of the “harder things for patients to endure.”

    A bespoke approach to hospital masking isn’t impractical. COVID waves won’t happen synchronously across communities, and so perhaps neither should policies. But hospitals that lack the resources to keep tabs on viral spread will likely be at a disadvantage, and Popescu told me she worries that “we’re going to see significant transmission” in the very institutions least equipped to handle such influx. Even the best-resourced places may hit stumbling blocks: Many are still reeling from three-plus years of crisis and are dealing with nursing shortages and worker burnout.

    Coordination hasn’t entirely gone away. In North Carolina, Duke is working with the University of North Carolina at Chapel Hill and North Carolina State University to shift policies in tandem; in Washington State, several regional health-care organizations have pledged to align their masking policies. And the Veterans Health Administration—where masking remains required in high-risk units—has developed a playbook for augmenting mitigations across its many facilities, which together make up the country’s largest integrated health-care system, says Shereef Elnahal, the undersecretary of Veterans Affairs for health. Still, institutions can struggle to move in sync: Attitudes on masking aren’t exactly universal across health-care providers, even within a hospital.

    The country’s experience with COVID has made hospitals that much more attuned to the impacts of infectious disease. Before the pandemic began, Talbot said, masking was a rarity in his hospital, even around high-risk patients; many employees would go on shifts sick. “We were pretty complacent about influenza,” he told me. “People could come to work and spread it.” Now hospital workers hold themselves to a stricter standard. At the same time, they have become intimately attuned to the drawbacks of constant masking: Some have complained that masks interfere with communication, especially for patients who are young or hard of hearing, or who have a language barrier. “I do think you lose a little bit of that personal bonding,” Talbot said. And prior to the lifting of universal masking at Vanderbilt, he said, some staff were telling him that one out of 10 times they’d ask a patient or family to mask, the exchange would “get antagonistic.”

    Read: The pandemic’s legacy is already clear

    When lifting mandates, many of the hospital epidemiologists I spoke with were careful to message to colleagues that the situation was fluid: “We’re suspending universal masking temporarily,” as Landon put it to her colleagues. Still, she admits that she felt uncomfortable returning to a low-mask norm at all. (When she informally polled nearly two dozen other hospital epidemiologists around the country in the spring, most of them told her that they felt the same.) Health-care settings aren’t meant to look like the rest of the world; they are places where precautions are expected to go above and beyond. COVID’s arrival had cemented masks’ ability to stop respiratory spread in close quarters; removing them felt to Landon like pushing those data aside, and putting the onus on patients—particularly those already less likely to advocate for themselves—to account for their own protection.

    She can still imagine a United States in which a pandemic-era response solidified, as it has in several other countries, into a peacetime norm: where wearing masks would have remained as routine as donning gloves while drawing blood, a tangible symbol of pandemic lessons learned. Instead, many American hospitals will be entering their fourth COVID winter looking a lot like they did in early 2020—when the virus surprised us, when our defenses were down.

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    Katherine J. Wu

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  • We Have a Mink Problem

    We Have a Mink Problem

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    Bird flu, at this point, is somewhat of a misnomer. The virus, which primarily infects birds, is circulating uncontrolled around much of the world, devastating not just birds but wide swaths of the animal kingdom. Foxes, bobcats, and pigs have fallen ill. Grizzly bears have gone blind. Sea creatures, including seals and sea lions, have died in great numbers.

    But none of the sickened animals has raised as much concern as mink. In October, a bird-flu outbreak erupted at a Spanish mink farm, killing thousands of the animals before the rest were culled. It later became clear that the virus had spread between the animals, picking up a mutation that helped it thrive in mammals. It was likely the first time that mammal-to-mammal spread drove a huge outbreak of bird flu. Because mink are known to spread certain viruses to humans, the fear was that the disease could jump from mink to people. No humans got sick from the outbreak in Spain, but other infections have spread from mink to humans before: In 2020, COVID outbreaks on Danish mink farms led to new mink-related variants that spread to a small number of humans.

    As mammals ourselves, we have good reason to be concerned. Outbreaks on crowded mink farms are an ideal scenario for bird flu to mutate. If, in doing so, it picks up the ability to spread between humans, it could potentially start another global pandemic. “There are many reasons to be concerned about mink,” Tom Peacock, a flu researcher at Imperial College London, told me. Right now, mink are a problem we can’t afford to ignore.

    For two animals with very different body types, mink and humans have some unusual similarities. Research suggests that we share similar receptors for COVID, bird flu, and human flu, through which these viruses can gain entry into our bodies. The numerous COVID outbreaks on mink farms during the early pandemic, and the bird-flu outbreak in Spain, gravely illustrate this point. It’s “not surprising” that mink can get these respiratory diseases, James Lowe, a veterinary-medicine professor at the University of Illinois at Urbana-Champaign, told me. Mink are closely related to ferrets, which are so well known for their susceptibility to human flu that they’re the go-to model for flu research.

    Mink wouldn’t get sick as often, and wouldn’t be as big an issue for humans, if we didn’t keep farming them for fur in the perfect conditions for outbreaks. Many barns used to raise mink are partially open-air, making it easy for infected wild birds to come in contact with the animals, sharing not only air but potentially food. Mink farms are also notoriously cramped: The Spanish farm, for example, kept tens of thousands of mink in about 30 barns. Viral transmission would be all but guaranteed in those conditions, but the animals are especially vulnerable. Because mink are normally solitary creatures, they face significant stress in packed barns, which may further predispose them to disease, Angela Bosco-Lauth, a biomedical-sciences professor at Colorado State University, told me. And because they’re often inbred so their coats look alike, an entire population may share a similar genetic susceptibility to disease. The frequency of outbreaks among mink, Bosco-Lauth said, “may actually have less to do with the animals and more to do with the fact that we raise them in the same way … we would an intensive cattle farm or chickens.”

    So far, there’s no evidence that mink from the Spanish farm spread bird flu to humans: None of the workers tested positive for the virus, and since then, no other mink farms have reported outbreaks. “We’re just not very susceptible” to bird flu, Lowe said. Our bird-flu receptors are tucked deep in our lungs, but when we’re exposed, most of the virus gets caught in the nose, throat, and other parts of the upper respiratory tract. This is why bird-flu infection is less common in people but is often pneumonia-level severe when it does happen. Indeed, a few humans have gotten sick and died from bird flu in the 27 years that the current strain of bird flu, known as H5N1, has circulated. This month, a girl in Cambodia died from the virus after potentially encountering a sick bird. The more virus circulating in an environment, the higher the chances a person will get infected. “It’s a dose thing,” Lowe said.

    But our susceptibility to bird flu could change. Another mink outbreak would give the virus more opportunities to keep mutating. The worry is that this could create a new variant that’s better at binding to the human flu receptors in our upper respiratory tract, Stephanie Seifert, a professor at Washington State University who studies zoonotic pathogens, told me. If the virus gains the ability to infect the nose and throat, Peacock, at Imperial College London, said, it would be better at spreading. Those mutations “would worry us the most.” Fortunately, the mutations that arose on the Spanish mink farm “were not as bad as many of us worried about,” he added, “but that doesn’t mean that the next time this happens, this will also be the case.”

    Because mink carry the receptors for both bird flu and human flu, they could serve as “mixing vessels” for the viruses to combine, researchers wrote in 2021. (Ferrets, pigs, and humans share this quality too.) Through a process called reassortment, flu viruses can swap segments of their genome, resulting in a kind of Frankenstein pathogen. Although viruses remixed in this way aren’t necessarily more dangerous, they could be, and that’s not a risk worth taking. “The previous three influenza pandemics all arose due to mixing between avian and human influenza viruses,” Peacock said.

    While there are good reasons to be concerned about mink, it is hard to gauge just how concerned we should be—especially given what we still don’t know about this changing virus. After the death of the young girl in Cambodia, the World Health Organization called the global bird flu situation “worrying,” while the CDC maintains that the risk to the public is low. Lowe said “it’s certainly not very risky” that bird flu will spill over into humans, but is worth keeping an eye on. H5N1 bird flu is not new, he added, and it hasn’t affected people en masse yet. But the virus has already changed in ways that make it better at infecting wild birds, and as it spreads in the wild, it may continue to change to better infect mammals, including humans. “We don’t understand enough to make strong predictions of public-health risk,” Jonathan Runstadler, an infectious-diseases professor at Tufts University, told me.

    As bird flu continues to spread among birds and in domestic and wild animal populations, it will only become harder to control. The virus, formally seasonal, is already present year-round in parts of Europe and Asia, and it is poised to do the same in the Americas. Breaking the chain of transmission is vital to preventing another pandemic. An important step is to avoid situations where humans, mink, or any other animal could be infected with both human and bird flu at the same time.

    Since the COVID outbreaks, mink farms have generally beefed up their biosecurity: Farm workers are often required to wear masks and protective gear, such as disposable overalls. To limit the risk to mink—and other susceptible hosts—farms need to reduce their size and density, reduce contact between mink and wild birds, and monitor the virus, Runstadler said. Some nations, including Mexico, Ecuador, have recently embraced bird-flu vaccines for poultry in light of the outbreaks. H5N1 vaccines are also available for humans, though they aren’t readily available.  Still, one of the most obvious options is to shut mink farms down. “We probably should have done that after SARS-CoV-2,” Bosco-Lauth, at Colorado State, said. Doing so is controversial, however, because the global mink industry is valuable, with a huge market in China. Denmark, which produces up to 40 percent of the world’s mink pelts, temporarily banned mink breeding in 2020 after a spate of COVID outbreaks, but the ban expired last month, and farms are returning, albeit in a limited capacity.

    But mink  are far from the only animal that poses a bird-flu risk to humans. “Frankly, with what we’re seeing with other wildlife species, there really aren’t any mammals that I would discount at this point in time,” Bosco-Lauth said. Any mammal species repeatedly infected by the virus is a potential risk, including marine mammals, such as seals. But we should be most concerned about the ones humans frequently come into close contact with, especially animals that are raised in high density, such as pigs, Runstadler said. This doesn’t pose just a human public-health concern, he said, but the potential for “ecological disruption.” Bird flu can be a devastating disease for wildlife, killing animals swiftly and without mercy.

    Whether bird flu makes the jump into humans, it isn’t the last virus that will threaten us—or mink. The era we live in has become known as the “Pandemicene,” as my colleague Ed Yong has called it, one defined by the regular spillover of viruses into humans, caused by our disruption of the normal trajectories of viral movement in nature. Mink may never pass bird flu to us. But that doesn’t mean they won’t be a risk the next time a novel influenza or coronavirus comes around. Doing nothing about mink essentially means choosing luck as a public-health strategy. Sooner or later, it will run out.

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    Yasmin Tayag

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  • What Happened to Hand-Washing?

    What Happened to Hand-Washing?

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    Way back in the early, whirlwind days of the pandemic, surfaces were the thing to worry about. The prevailing scientific wisdom was that the coronavirus spread mainly via large droplets, which fell onto surfaces, which we then touched with our hands, with which we then touched our faces. (Masks, back then, were said by public health authorities to be unnecessary for the general public.) So we washed our hands until they were raw. We contorted ourselves to avoid touching doorknobs. We went through industrial quantities of hand sanitizer, and pressed elevator buttons with keys and pens, and disinfected our groceries and takeout orders and mail.

    And then we learned we’d had it all backwards. The virus didn’t spread much via surfaces; it spread through the air. We came to understand the danger of indoor spaces, the importance of ventilation, and the difference between a cloth mask and an N95. Meanwhile, we mostly stopped talking about hand-washing. The days when you could hear people humming “Happy Birthday” in public restrooms quickly disappeared. And wiping down packages and ostentatious workplace-disinfection protocols became a matter of lingering hygiene theater.

    This whole episode was among the stranger and more disorienting shifts of the pandemic. Sanitization, that great bastion of public health, saved lives; actually, no, it didn’t matter that much for COVID. On one level, this about-face should be seen as a marker of good scientific progress, but it also raises a question about the sorts of acts we briefly thought were our best available defense against the virus. If hand-washing isn’t as important as we thought it was in March 2020, how important is it?

    Read: Don’t worry, it’s not COVID

    Any public-health expert will be quick to tell you that, please, yes, you should still wash your hands. Emanuel Goldman, a microbiologist at Rutgers New Jersey Medical School, considers it “commonsense hygiene” for protecting us against a range of viruses spread through close contact and touch, such as gastrointestinal viruses. Also, let’s be honest: It’s gross to use the bathroom and then refuse to wash, whether or not you’re going to give someone COVID.

    Even so, the pandemic has piled on evidence that the transmission of the coronavirus via fomites—that is, inanimate contaminated objects or surfaces—plays a much smaller role, and airborne transmission a much larger one, than we once thought. And the same likely goes for other respiratory pathogens, such as influenza and the coronaviruses that cause the common cold, Linsey Marr, an environmental engineer and aerosols expert at Virginia Tech, told me.

    This realization is not an entirely new one: A 1987 study by researchers at the University of Wisconsin found that a group of men playing poker with “soggy,” rhinovirus-contaminated cards were not infected, while a group playing with other sick players were. Now Goldman intends to push this point even further. At a conference in December, he is going to present a paper arguing that, with rare exceptions, such as RSV, all respiratory pathogens are transmitted predominantly through the air. The reason we’ve long thought otherwise, he told me, is that our understanding has been founded on faulty assumptions. Generally speaking, the studies pointing toward fomite-centric theories of transmission were virus-survival studies, which measure how long a virus can survive on a surface. Many of them either used unrealistically large amounts of virus or measured only the presence of the virus’s genetic material, not whether it remained infectious. “The design” of these experiments, he said, “was not appropriate for being able to extrapolate to real-life conditions.”

    The upshot, for Goldman, is that surface transmission of respiratory pathogens is “negligible,” probably accounting for less than .01 percent of all infections. If correct, this would mean that your chance of catching the flu or a cold by touching something in the course of daily life is virtually nonexistent. Goldman acknowledged that there’s a “spectrum of opinion” on the matter. Marr, for one, would not go quite so far: She’s confident that more than half of respiratory-pathogen transmission is airborne, though she said she wouldn’t be surprised if the proportion is much, much higher—the only number she would rule out is 100 percent.

    Read: The very real lessons America has learned from COVID

    For now, it’s important to avoid binary thinking on the matter, Saskia Popescu, an epidemiologist at George Mason University, told me. Fomites, airborne droplets, smaller aerosol particles—all modes of transmission are possible. And the proportional breakdown will not be the same in every setting, Seema Lakdawa, a flu-transmission expert at Emory University, told me. Fomite transmission might be negligible at a grocery store, but that doesn’t mean it’s negligible at a day care, where kids are constantly touching things and sneezing on things and sticking things in their mouths. The corollary to this idea is that certain infection-prevention strategies prove highly effective in one context but not in another: Frequently disinfecting a table in a preschool classroom might make a lot of sense; frequently disinfecting the desk in your own private cubicle, less so.

    Much of the conspicuous cleaning we did early in the pandemic was excessive, Popescu said, but she worries that we may have slightly overcorrected, lumping some useful behaviors—targeted disinfection, even hand-washing in some cases—into the category of hygiene theater. Whatever the setting, the experts I spoke with all agreed that these behaviors remain important for contending with non-respiratory pathogens. Recently, when several members of Marr’s family came down with norovirus, an extremely unpleasant stomach bug that causes vomiting, diarrhea, and stomach cramping, she disinfected a number of high-touch surfaces around the house. Picture that: one of the country’s foremost experts on airborne transmission wiping down doorknobs and light switches.

    Marr isn’t convinced we’ve overcorrected. Hand sanitizer still abounds, businesses still tout their surface-cleaning protocols, and air quality still gets comparatively little attention. Recently, she watched a person use their shirt to open the door of a visitor center without touching the handle … then proceed inside unmasked. There’s nothing wrong with taking certain precautions to prevent fomite transmission, she said—these should not all be dismissed en masse as hygiene theater—as long as they don’t come at the expense of efforts to block airborne transmission. “If you’re doing extra hand washing … then you should also be wearing a good mask in crowded indoor environments,” Marr said. “If you’re bothering to clean the surfaces, then you should be bothering to clean the air.”

    On Friday, with respiratory-virus season looming, CDC Director Rochelle Walensky tweeted out three pieces of advice for staying healthy: “Get an updated COVID-19 vaccine & get your annual flu vaccine,” “Stay home if you are sick,” and—not to be forgotten—“Practice good hand hygiene.” She made no mention of masks or ventilation.

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    Jacob Stern

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