The second wave has reached the region’s most vulnerable.

Amid soaring coronavirus caseloads in Maryland, Virginia and D.C., some nursing homes have begun to report explosive new outbreaks of the novel coronavirus among residents and staff, affirming the worst fears of family members and health officials.

Despite stringent shutdown measures in place since March, widespread community transmission has allowed the highly contagious virus to creep back into facilities through asymptomatic employees, threatening the elderly residents most at risk of dying.

The spike in cases in Virginia, Maryland and D.C. since August has not yet been followed by a notable surge in deaths. But health experts note that fatalities often lag several weeks behind new infections, and warn that the uncontrolled spread of the virus in nursing homes could lead to a significant jump in deaths of covid-19, the disease caused by the virus.

In rural localities, a large outbreak at even one long-term care facility could tip the health system into chaos.

Some government officials are alarmed. Maryland Gov. Larry Hogan (R) on Tuesday severely limited indoor visitation at nursing homes and announced that all facilities must test staff twice a week. Maryland health officials also say they are ramping up on-site visits and doubling the number of employees dispatched to nursing homes as “rapid response teams.” County officials say they’re stockpiling masks and gowns, concerned that the nationwide surge in cases will again disrupt supply chains, as happened this past spring.

Nursing homes are better prepared now than they were nine months ago, experts say, but some challenges — such as shortages of staff and protective equipment — persist. Systemic problems, including low wages, mean that many nursing homes are still relying on contract employees to fill shifts, inadvertently enabling the spread of the virus.

“We never truly fixed the problems,” said Jennifer Nuzzo, an epidemiologist at the Johns Hopkins Center for Health Security. “There were just a lot of Band-Aids.”

In Virginia, at least 200 staff members and 380 residents have contracted the virus since the start of November, officials say. A disproportionate number of outbreaks are in the southwest part of the commonwealth, where ­cases have been skyrocketing. In Roanoke City, where test positivity is higher than 10 percent, nine of 11 long-term care facilities have active outbreaks.

In Maryland, new weekly infections among residents and staff members at long-term care facilities have increased tenfold since the start of October, according to a Washington Post analysis of state data. The state went from reporting 76 new cases in the first week of October to 267 in the first week of November — and 1,012 this week.

The Hebrew Home of Greater Washington — Maryland’s largest nursing home, with 558 certified beds — is among five facilities in Montgomery County that have reported significant jumps in new infections, said Enrico Lachica, a clinical nurse administrator at the county’s Department of Health and Human Services.

After nearly five months of between zero to two cases each week, the Rockville facility recorded 26 new infections among residents on Oct. 28. Within the span of three weeks in October and November, 101 staff members and residents tested positive for the coronavirus, exceeding the home’s previous peak of 68 new cases in May.

Sara McAlpin, a 96-year-old who suffers from dementia, is among the newly infected. Late last week, the usually responsive woman appeared lethargic, “as though she was in a deep sleep,” said daughter Derede McAlpin.

When a nurse practitioner called last week to say that her mother had tested positive, the younger McAlpin said she was heartbroken but not surprised.

“All this time, I’ve been increasingly concerned because of the understaffing,” she said. Since the pandemic began, many of her calls to the facility have gone unanswered, she added, and when she does hear from a nurse, they often say that they are being stretched thin because of staffing shortages.

Brenda L. Rice, a vice president of the nonprofit group that runs the nursing home, said in a statement that employees have been tested on a weekly basis per a state mandate. When asked how the virus may have entered the facility, Rice referred to research showing that high levels of community spread can often lead to nursing home outbreaks.

“We remain vigilant in making any necessary adjustments recommended by health officials moving forward as the care of our residents remains our top priority,” her statement said.

State and county officials have visited the Hebrew Home multiple times in recent weeks to help with the outbreak, Lachica said.

Nuzzo, the Hopkins scientist, said that regular testing and robust infection-control measures can lower the chance of transmission but are not foolproof. Nursing homes “do not exist in bubbles,” she said. “They are part of the community.”

Joseph DeMattos, president of the Health Facilities Association of Maryland, said part of the uptick in cases is because of the “covid fatigue” that has driven people to let down their guard in terms of mask-wearing and physical distancing in the community.

For McAlpin, seeing people crowd inside restaurants and stores this fall was jarring. As a Black person, she said, she has seen the virus decimate her community, killing at least three of her friends’ parents. She said she empathizes with the poor labor conditions faced by nursing home employees, who argued in September that it was premature for Maryland to move into Phase 3 of its reopening.

“The virus has touched some communities more than others,” McAlpin said. “I knew it could return at any time.”

In rural Smyth County in southwest Virginia, Valley Health Care Center kept the virus at bay for more than five months. Then, in August, the first resident tested positive after returning from a hospital in Charlottesville.

“It basically exploded from there,” administrator Jason Lindsey said. For six consecutive weeks, between 18 and 30 residents tested positive. By October, there were 173 cases associated with the facility, according to the state Health Department.

The nursing home has been free of covid-19 for the past month, but Lindsay said he is worried about what will happen as employees return from holiday celebrations.

Trained nursing home employees were scarce even before the pandemic, experts say. Now, hundreds of them across the region are being forced to quarantine after testing positive for the disease.

“The supply isn’t keeping pace with demand,” said Amy Hewett, a spokeswoman for the Virginia Health Care Association.

D.C. has so far managed to avoid a second spike in cases at nursing homes, a feat that industry advocates attribute in large part to regular, government-funded testing for all employees. In the first two weeks of November, fewer than 10 new infections were reported among residents of the city’s 19 long-term care facilities.

Virginia has mostly asked nursing homes to pay for their own employee testing since the start of the pandemic, and Maryland stopped paying for it in August, prompting frustration from some facilities that said they couldn’t afford to foot the bill.

The federal Centers for Medicaid and Medicare Services (CMS) released guidance in July saying that nursing homes should test employees based on the test positivity rate in their community. So, as test positivity in some parts of Maryland and Virginia declined this fall, some nursing homes tested workers less frequently than they had in the summer.

“The District government did the right thing,” said Veronica Sharpe, president of the D.C. Health Care Association. “Are there hiccups and things that could have been done better? Yes. But overall, the District has been a model.”

Maryland told nursing homes last week to start testing all employees twice weekly — once with a polymerase chain reaction (PCR) test, which takes several days to show results, and once with a rapid point-of-care test, which the state will help to supply through the end of the year.

DeMattos said orchestrating the tests “won’t be easy to execute or to fund, but it is the right thing to do.”

Hewett said the vast majority of nursing homes in Virginia are testing staff at least once a week because positivity rates across the state have ticked upward of 5 percent, triggering the federal guidance. The guidance suggests testing staff twice a week if the positivity rate in a county exceeds 10 percent.

As of last week, Maryland ranked 15th in the country in terms of covid-19 mortality at nursing homes, with about 62 deaths per 1,000 residents, CMS data shows. The District was 17th in the country with 61 deaths per 1,000 residents, and Virginia was 24th, with 52 deaths per 1,000 residents.