Health officials in New York, California and other hard-hit parts of the country are restricting coronavirus testing to health care workers and the severely ill, saying the battle to contain the virus is lost and the country is moving into a new phase of the pandemic response.

As cases spike sharply in those places, they are bracing for an onslaught and directing scarce resources where they are needed most to save people’s lives. Instead of encouraging broad testing of the public, they’re focused on conserving masks, ventilators and intensive care beds - and on getting still-limited tests to health-care workers and the most vulnerable. The shift is further evidence that rising levels of infection and illness have begun to overwhelm the health care system.

A similar message was hammered Saturday by members of the White House coronavirus task force, who said it was urgent to conserve scarce supplies and offered guidelines about who should get tested. Top priority, they said, should go to those who are hospitalized, along with health-care workers, symptomatic residents of long-term care facilities and people over 65 - especially those with heart and lung disease, which place them at higher risk.

“Not every single person in the U.S. needs to get tested,” said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. “When you go in and get tested, you are consuming personal protective equipment, masks and gowns — those are high priority for the health care workers who are taking care of people who have coronavirus disease.”

Health officials are now struggling with a complicated and shifting message. More people can get tested as drive-through sites open and more tests are finally available. Nevertheless, those with mild symptoms should stay home and isolate. And everyone should practice social distancing to preserve the health care system’s finite resources.

To convey those points clearly, many officials are speaking in increasingly blunt terms, saying that wide testing could jeopardize the lives of health care workers and the U.S. response by burning through precious supplies as a tidal wave of sick people descend on the system.

“In a universe where masks and gowns are starting to become scarce, every time we test someone who doesn’t need one, we’re taking that mask and gown away from someone in the intensive care unit,” said Demetre Daskalakis, deputy commissioner for the Division of Disease Control of the New York City Department of Health and Mental Hygiene.

The tactical and messaging shifts come after weeks of efforts to expand access to testing after the federal government’s botched rollout, which hampered states’ ability to know whether the virus was already circulating and to take steps to get ahead of it.

Millions more tests are now available. And the Food & Drug Administration on Friday approved the first coronavirus test that can deliver results in 45 minutes. The turnaround time is far faster than for current tests, which are typically sent to centralized labs and can take days to return results.

The FDA granted “emergency use authorization” to Cepheid, a California company that makes a rapid molecular test, for use in “patient care settings,” but the company and the FDA said initially it will be used in hospitals, emergency rooms and urgent care centers.

The test will “help alleviate the pressure” on health-care facilities by helping doctors find out quickly whether a patient has the disease and select the appropriate treatment, David Persing, Cepheid’s chief medical and technology officer, said in an interview.

Despite those developments, however, many health officials remain concerned that testing sites will be inundated and that the president’s previous assertions that anyone who wanted a test “could have one” will lead many with mild cases to squander finite resources.

“I’m just scared there’s going to be mass confusion when people find out there is a testing site, are worried about their covid status, and they’re going to mob the testing site,” said Michael Fraser, executive director of the association that represents state health directors. “It’s confusing to people to hear that testing is being made available in a much more convenient way, and they think, ‘Hey, this is great, let’s get tested.’ ”

New York City’s Daskalakis said people with a manageable fever and cough who aren’t at high risk for severe illness should assume they have covid-19. Seeking a test exposes health care workers administering them and wastes resources, since nothing would change for those individuals based on their results, he said. There is no approved treatment for the disease.

A “negative” test could also provide false reassurance as covid-19 has become widespread, he said. When one of his patients with symptoms -who sought a test against his advice -got a negative result, Daskalakis told the person to presume he had the disease anyway and to isolate himself.

New York’s Mount Sinai Hospital, which treated the state’s first coronavirus case, is testing only a minority of the hundred-plus patients with respiratory symptoms who come to the emergency department each day, said Jolion McGreevy, the emergency department medical director.

“The default assumption is yes -anyone who comes in with any kind of fever, cough, respiratory symptom, flu-like illness, we’re making the assumption that they have this,” he said, based on the prevalence of community transmission in New York. “It’s very likely you have it. There’s no benefit for you to test.”

Other county and state health officials are sounding similar warnings, weeks after federal officials announced 1.1 million tests had been shipped out and another 4 million were coming.

Los Angeles County health officials advised doctors in a letter Thursday to give up on testing patients as a strategy to contain the outbreak, instructing them to test patients only if a positive result could change how they would be treated, the Los Angeles Times reported. The department “is shifting from a strategy of case containment to slowing disease transmission and averting excess morbidity and mortality,” according to the letter.

That same day, Sacramento county officials ordered residents to stay home except for essential activities, part of the city’s evolving strategy away from efforts to contain the virus by identifying and isolating each case and tracing that person’s contacts -a laborious process that becomes all but impossible once cases mount. The health order said the intent is to protect the most vulnerable, slow the virus’ spread, and preserve the ability of front-line workers to care for severely ill patients.

In Washington state, where hospital workers have been fashioning makeshift protective medical gear using parts purchased from Home Depot and craft stores, officials are restricting testing to high-risk populations, including health care workers and people with more severe symptoms.

“We’ve asked the public to understand we can’t test everyone, especially if they have mild symptoms or are asymptomatic,” said Jeff Duchin, health officer for Seattle and King County, a hard-hit part of the country.

It’s a trade-off between individual and societal good that Americans are not used to making. A test result may be reassuring to individuals who feel unwell, but the mask and health care worker to test someone with mild symptoms are resources that could be used to save someone’s life.

“In developing countries, we only recommend testing if it changes how you manage the care of an individual person,” said a public health official who has worked in the U.S. and Africa who requested anonymity because he was not authorized to speak. “I know it would make you feel better to know what you really have, but it doesn’t change your individual care.”

In an ideal world, public health officials say they should have done wide-scale surveillance testing of people with respiratory symptoms much earlier. But city-by-city and state-by-state, they are nearing -or in some cases have already crossed -the line when they must make touch choices.

“In the 2009 influenza pandemic, we stopped testing for H1N1 once the level of illness in the community was so high that it just made more sense to treat based on clinical symptoms,” said Jennifer Nuzzo, an epidemiologist with the Johns Hopkins Bloomberg School of Public Health’s Center for Health Security.

While she said it’s essential for testing capacity to increase, “we have to target our resources and reserve testing for those who need it most: the severely ill and those in high risk professions, such as health care workers.

“We’d cause more harms by encouraging the general public to run out and get tested if they are well or experiencing mild illness,” Nuzzo said.