SEATTLE—Just after sunset Monday evening, a line of homeless men about a half-block long waited for a dinner of tacos and nachos dished out by three gloved servers in front of the Union Gospel Mission. The faith-based nonprofit, which began serving soup to homeless and unemployed people during the Great Depression, runs a men’s shelter out of a historic six-story brick building in Seattle’s downtown Pioneer Square neighborhood.

A short walk away, Lucy, 31, and her husband John, 32, were sorting through their belongings in City Hall Park. The couple, who like other homeless individuals in this story declined to give their last names, were preparing to spend yet another night under the Yesler Way overpass a block away, where they had spent the past three weeks, they said. The nighttime low was expected to drop into the mid-30s, and they longed for the warmth of their previous home in Tucson, Ariz.

Both said they had been sick for several weeks, with symptoms that included nausea, diarrhea, weakness, and coughing fits. Maybe it was the stomach flu; maybe something more serious. “I’ve been coughing up the GEICO lizard and I don’t even have insurance,” Lucy quipped.

Amid an ongoing homelessness crisis driven by a critical lack of affordable housing in this tech boomtown, a new threat is sorely testing the city’s ability to administer to those in need: the growing epidemic of 2019 novel coronavirus that has already sickened at least 190 people and killed at least 22 in King County alone.

But it’s not just a Seattle problem. The United States has long struggled to adequately feed, shelter, and care for a homeless population conservatively estimated at about 570,000 even in the best of circumstances. Now the COVID-19 epidemic threatens not only to endanger some of the most vulnerable people in the country, but also cause a new breakdown in efforts to diagnose, treat, and isolate infected patients.

That, in turn, could help refashion a homelessness crisis advocates say has long been ignored as an urgent problem for everyone—from middle-class workers to the 1 percent.

“Our fates are tied together, whether we want to acknowledge it or not,” said Giridhar Mallya, a public health physician and senior policy officer at the Princeton, N.J.-based Robert Wood Johnson Foundation. “I think a public health crisis like this lays bare the social inequities that we tolerate every day, but that then become that much more acute when you’re trying to keep people from getting sick or keep sick people from making other people sick.”

So far, U.S. health officials haven’t confirmed major COVID-19 outbreaks in the homeless population. But experts say that’s likely only a matter of time. “We are worried that when—probably not if—COVID spreads into this population, efforts at infection control are going to be very, very challenging,” said Margot Kushel, professor of medicine and director of the Center for Vulnerable Populations of at the University of California at San Francisco.

Health experts have been warning that the arrival of COVID-19 in a homeless shelter could be even more disastrous than, say, on a cruise ship given the close contact and crowding among overnight residents. Many of them are also older, have underlying health conditions, and often lack soap or sanitizer to clean their hands or potentially contaminated surfaces.

Amy Hagopian, a professor of global health at the University of Washington in Seattle, agreed that the growing COVID-19 crisis was making clear risks normally associated with poorer communities can endanger the wealthy, as well. “These viruses are powerful, pesky things,” she said. “And if we want to all be healthy, we need to worry about those with the least resources.”

Last week, New York City, officials said schools would close only as a “last resort” due to COVID-19 because an estimated 114,000 homeless students would otherwise have nowhere to go for meals or medical care. Many schools have become de facto social service centers in the absence of other infrastructure for kids and their parents, complicating “social distancing” strategies intended to prevent or slow community transmission of the coronavirus. Although children have so far appeared to be less impacted by the resulting disease than older adults, studies suggest they can still be carriers.

Public officials aren’t ignoring the problem, though their responses have ranged widely. On Tuesday, San Jose, Calif., Mayor Sam Liccardo said regular “sweeps” of homeless camps would be at least temporarily halted because of the outbreak. Meanwhile, San Francisco announced $5 million in new funding aimed primarily at regularly cleaning its shelters and supportive housing to reduce the risk of transmission there.

But even when there’s money and resources to try to rein the problem in, an outbreak like COVID-19 makes things complicated. Seattle Homeless Outreach, a nonprofit that brings basic survival, hygiene, and pet food supplies to homeless people and provides them with harm-reduction tools like condoms and collection containers, canceled planned outreach this week to reduce the risk of the virus spreading. On its website, Union Gospel Mission likewise announced plans to curtail volunteer opportunities through the end of March as a precaution against the spread of a virus that can passed on through mucus or saliva droplets and contaminated surfaces.

Some experts worry that any cases could provoke more stigma against an already marginalized group and further reduce volunteering. In other words, a vicious cycle of disengagement at the worst possible time.

In Seattle and King County, officials have responded by opening new shelters to create more room for precautions to slow the spread of any infection. Two new locations with room for 100 people opened last week, and a third opened Monday evening, which allowed providers to transfer people from other locations. “Just like hospitals are thinking about surge capacity, cities and counties need to be thinking about surge capacity for folks that are homeless or without a shelter,” Mallya said.

Public health officials also may need to raise the threshold on admitting homeless people to hospitals to avoid overtaxing healthcare facilities, taking up valuable bed space, or unnecessarily exposing them to the coronavirus, Kushel said. But that means homeless patients may have a more difficult time getting their other healthcare needs addressed, which could lead to more medical emergencies or worsening conditions that still leave them more vulnerable to the virus. “It’s just a terrible situation,” she said.

Their care is further complicated by high rates of mental illness and addiction—the main factors driving a sharp increase in recent hospitalization rates among the homeless.

There’s yet another barrier to addressing the COVID-19 crisis, however. Despite the high vulnerability of the homeless population, public health officials may have a difficult time breaking through the rampant distrust, denial, and misinformation.

One man in front of the Union Gospel Mission asserted that the line of people waiting for their dinner had been living outside for so long that their strengthened immune systems would make them less likely to fall ill than downtown office workers. “I just kicked MRSA’s ass!” the man said, pointing to a scar between his left thumb and forefinger where a methicillin-resistant Staphylococcus aureus infection had recently healed. “I ain’t getting sick with nothing else.”

Lucy, who is HIV-positive but sometimes doubts her diagnosis, said she has nonetheless endured multiple medical crises, including gastrointestinal stromal tumors and two collapsed lungs, which have weakened her immune system and left her more vulnerable. But both she and her husband questioned whether they were really at risk for COVID-19.

John said they had been using hand sanitizer, but hadn’t received any information about what to look for and lacked a thermometer to check each other’s temperature for a fever anyway. From multiple bad experiences with the healthcare system, Lucy said, she was terrified of doctors and would be reluctant to go to a hospital if she developed symptoms. “I want and need a doctor that I can trust,” she said.

Their friend Steve, bundled up in multiple jackets and a red knit cap, sat listening to the conversation, and then asked if he needed to worry about the virus because of his age. He is 65.

When told that older people are at greater risk, he fell silent.