Care facilities can’t keep the virus out as it spreads through communities.

The coronavirus is surging in nursing homes once again, despite President Donald Trump’s promise to keep vulnerable residents of care facilities safe while encouraging most people to work, play, shop and attend school normally.

Covid-19 cases in nursing homes saw a more than 40 percent increase from mid-September to Oct. 25 after seven weeks of steady decline, according to the most recent data. Nursing home operators and experts on long-term care say it’s basically impossible to keep the coronavirus from seeping in as cases spike in communities across the country.

The administration has improved testing and staff screenings at nursing homes since last spring, yet workers will inevitably bring the virus in with them. But Trump has repeatedly downplayed the virus while sidelining federal health officials, such as the nation’s top infectious disease expert Anthony Fauci, as cases surge across the country.

“As cases in the community increase, this highly contagious virus finds its way into our buildings,” said Mark Parkinson, the head of the major nursing home lobby, the American Health Care Association.

The new infections in care facilities are creating a growing challenge for President-elect Joe Biden, who pledged special attention to nursing homes, including contact tracing in every facility and fully invoking the Defense Production Act to increase the supply of key protective gear.

But Biden, too, will face challenges in a divided, distrustful virus-fatigued nation. He has announced a coronavirus advisory group to start work immediately, aiming for a coordinated, national response using the basic tools of public health like contact tracing, masks and comprehensive testing. Even with the progress toward a vaccine announced by Pfizer on Monday, experts say those public health steps will be the best ways of combating the virus because it will take months to make the vaccine widely available.

The pattern in nursing homes is clear. During each period of heightened community spread, cases in nursing homes have consistently climbed. It is not currently as bad as it was at the onset, when testing was negligible, the virus’s silent spread in the U.S. was underestimated, and doctors knew less about how to treat it. But the risks rise in nursing homes as cases soar outside nursing homes, and as hospitals and ICUs fill up.

The cases “in long-term care facilities essentially mirrored what was happening nationally, what was happening in communities around long-term care facilities,” said Priya Chidambaram, a policy analyst at the Kaiser Family Foundation.

Last week, Indiana began deploying the National Guard to help nursing homes with testing, reporting results and screening employees. Nursing homes in places such as Oklahoma are facing a workforce shortage as staff either get sick or go into quarantine after being exposed. Wisconsin reported 112 long-term care facilities with new coronavirus outbreaks in the past week, nearly double the prior week’s increase, according to The Atlantic’s Covid Tracking Project blog.

Staff members unwittingly carrying the virus into nursing homes is a big source of spread.

“The bottom line is our staff leave every day. They’re out in the community,” said Mary Brinkley, the executive director of LeadingAge Oklahoma, which represents nonprofit providers of aging services.

Across the country, nearly 15 percent of nursing home providers say they have less than one week of supply of at least one type of key personal protective equipment, such as gloves or masks. About 22 percent have a shortage of any staff, such as nurses, aides and clinical workers, according to a POLITICO analysis of the latest Centers for Medicare and Medicaid Services data from Oct. 25.

“Our members need more support to keep older adults and the people who care for them in nursing homes and other settings safe,” said Katie Smith Sloan, the president and CEO of LeadingAge.

The mainstream view in the public health community is the Trump White House’s approach of downplaying rising caseloads understates who is at high risk. Seniors who don’t live in nursing homes or assisted living, as well as millions of younger people with chronic conditions like obesity, heart disease and diabetes, are also acutely susceptible to the virus. And while young people have much better odds, some do become seriously ill, and some have died. The risks are even higher for Black people, Latinos and Native Americans.

The Trump administration has denied it is aiming to reach “herd immunity” before a vaccine — a term that’s generally used to describe a societywide level of protection through vaccination, not through the spread of a dangerous disease. But Trump has often encouraged most Americans to go about their lives while promising to protect high-risk groups.

White House spokesperson Sarah Matthews said in a recent statement, “We remain intensely focused on ensuring communities have the tools and resources to better treat patients and protect the most vulnerable — especially our nation’s seniors and nursing homes” while protecting the country from harmful lockdowns. She pointed to the Trump administration’s effort earlier this year to send rapid coronavirus tests to the nation’s roughly 15,000 nursing homes and deploy strike teams to facilities with high case counts.

Trump administration officials have met with a trio of scientists pushing for “focused protection” outlined in a document they wrote called the “Great Barrington Declaration,” which has been publicly criticized by many mainstream public health experts and which Fauci has called “total nonsense.” That means letting the virus spread among healthy people while shielding those at high risk. Scott Atlas, Trump’s current favored health adviser, largely shares those views.

One of those scientists, Martin Kulldorff, a Harvard professor of medicine, said a slate of policies for nursing homes should include even more frequent testing of nursing home staff and not letting staff work in other facilities. Another co-author, Jayanta Bhattacharya, a Stanford medical professor, said the stay-at-home approach initially used last March and April didn’t work. “Relying on limiting community spread via lockdowns to protect nursing homes is a failed strategy that has led to the needless deaths of tens of thousands of older people in the US and many more around the world,” he wrote in an email.

Critics argue that the “lockdowns,” which the administration called stay-at-home orders, were not enforced by all states. They also say Trump is wrong to assert that the virus will disappear.

“The premise is that a virus can infect enough people in the population to provide immunity so that essentially the virus would put itself out of business. That has never happened. That’s never happened for any virus,” said Paul Offit, one of the nation’s top vaccine experts at the University of Pennsylvania and a high-profile critic of the Trump pandemic policies.

Tucker Doherty contributed to this report.

This article was written with the support of a journalism fellowship from The Gerontological Society of America, The Journalists Network on Generations and The John A. Hartford Foundation.