As concerns about the coronavirus mount, Bay Area experts are worrying about what will happen if the infection strikes the region’s most vulnerable residents: the homeless.

Tent and RV encampments, where residents tend to be packed tightly together in unsanitary conditions, could provide an ideal breeding ground for the new COVID-19 virus sweeping the globe. Typical precautionary measures — such as avoiding close contact with others, self-isolating when you’re sick and washing hands frequently — are all but impossible in encampments with no solid walls or running water.

If they are infected, homeless people face a higher risk of getting very sick from the disease, experts say. They tend to be older, and their immune systems already may be compromised by other chronic illnesses, drug or alcohol use, and the harsh realities of street living.

It could become a major problem throughout California, which not only has more confirmed cases of coronavirus than any other state, but also holds the nation’s largest population of homeless residents. And thousands of those unhoused people are in the Bay Area.

“I think we’re all worried about it,” said Dr. Margot Kushel, director of the UCSF Center for Vulnerable Populations at Zuckerberg San Francisco General Hospital.

The worry has become more pronounced in recent days. The public learned a Solano County resident appears to be the nation’s first coronavirus patient to contract the illness from an unknown source, amplifying concerns that the virus will start spreading within the state.

So far, the agencies and nonprofits tasked with taking care of the Bay Area’s homeless seem to be watching, planning and waiting, but have yet to reveal specific new policies to protect the unhoused. A California Department of Public Health representative said the agency is monitoring the situation.

“Persons experiencing homelessness are not likely to have any particular risk for COVID-19 related to international travel or exposure to recent travelers,” a spokeswoman wrote in an emailed statement. “However, as the situation evolves, the California Department of Public Health and local health departments in California will engage with groups at risk of exposure and provide information on how people can best protect their health.”

As soon as the CDC on Tuesday warned Americans that it’s not a matter of if the coronavirus will spread within the U.S., but when, the Community Services Agency of Mountain View and Los Altos began working on a plan to protect its clients, staff and volunteers, said Executive Director Tom Myers. The agency provides aid to the homeless, low-income families and seniors, and Myers worries about the virus spreading through all three of those populations.

His team’s prevention plan, which he hopes to have ready by Monday, may include precautions such as changing the way the agency operates its food pantry program — a service that draws hundreds of people every day. Workers might start donning masks and gloves before handing out food, he said. And they might begin pre-bagging food and distributing it outside the center to reduce foot traffic through the building.

“Quite frankly, we feel like we need to be incredibly proactive on this and look at what is a worst-case scenario,” Myers said.

The staff at Bay Area Community Services, an Oakland-based nonprofit, is waiting for guidance from the public health sector, said Daniel Cooperman, director of housing strategy.

“It’s obviously impacting the whole world at this point,” he said, “so it’s something we’re closely monitoring and worried about.”

The Alameda County Public Health Department is “considering the unique needs of our unhoused populations,” spokeswoman Neetu Balram wrote in an emailed statement.

“From our experience with previous outbreaks, curbing the spread of disease is a community effort and we will need the partnership of our cities and nonprofits,” Balram wrote. “We will share updated guidance with our partners as it becomes available, and will work with them to safeguard all of our communities.”

In Santa Clara County, a health department spokeswoman said the agency is working with local service providers to make sure information about health recommendations and emergency notifications reach the homeless.

For some experts, coronavirus brings to mind the hepatitis A outbreak that tore through California encampments in 2016 and 2017. After igniting in San Diego County, the disease — which can spread through close personal contact or via food and drinks contaminated with small amounts of infected stool — traveled up and down the coast, sickening more than 700 people and killing 21, according to the CDC. Bay Area Community Services quickly mobilized with county health care officials to vaccinate as many East Bay homeless residents as possible. And it worked — the outbreak largely missed the region, Cooperman said.

But there’s one big difference between coronavirus and hepatitis A: There’s no vaccine for coronavirus.

If the virus continues to spread, Kushel predicts agencies will distribute hand sanitizer and install more hand-washing stations in encampments. Hospitals also could lower their admission thresholds, she said, accepting people who have no home to rest, recuperate and self-quarantine in, even if they have minimal symptoms.

“Honestly, I think it’s going to be very challenging,” Kushel said.

Kushel also worries the coronavirus outbreak will be dangerous in other ways for the homeless even if they don’t get sick.

“My fear,” she said, “is that this will be used as another way to further stigmatize an already stigmatized and challenged population.”