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.

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.

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.”

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.