With coronavirus infections soaring across the nation, federal health officials on Friday urged Americans in the most forceful language yet to take steps to protect themselves — starting with consistent, proper use of masks — and pressed local governments to adopt 10 public health measures deemed necessary to contain the pandemic.
The guidance reflected deep concern at the agency that the pandemic is spiraling further out of control and that many hospitals are reaching a breaking point, potentially disrupting health care across the country.
Agency officials have issued increasingly stark warnings in the waning weeks of the Trump administration, and President-elect Joseph R. Biden Jr. has promised a new national strategy to turn back the virus. On Thursday, Mr. Biden said he would call on Americans to wear facial coverings for 100 days.
To some experts, the C.D.C.’s appeal appeared to augur a more comprehensive and coordinated national approach to controlling the pandemic — one consistent with messages from Mr. Biden and his advisers.
“We’re seeing C.D.C. and other public health institutions awaken from their politics-induced coma,” said Dr. Thomas R. Frieden, who served as the agency’s director under President Barack Obama.
“This is them aligning themselves more with science, which also aligns them more with the Biden administration,” he added.
While none of the directives are new, experts said the rising case numbers demonstrated a need for a more uniform approach, rather than the patchwork of restrictions adopted by states.
“The role of the C.D.C. is to lead with the science,” said Dr. Celine Gounder, an infectious-disease physician and member of Mr. Biden’s Covid advisory group. “In the absence of strong national guidance from the C.D.C., we’ve had a variety of responses across the country, some more scientifically grounded than others.”
The scientific evidence supporting the effectiveness of certain health measures, such as wearing masks, has been accumulating, and those measures are urgently needed now to stop the spread, C.D.C. officials said.
Though the agency has issued all of the recommendations in earlier guidance, the new summary represented the first time the C.D.C. had published a multipronged list of strategies for states, a sort of battle plan.
“This idea of a 50-state solution is completely impractical when we live in one nation,” said Jennifer Nuzzo, an epidemiologist at Johns Hopkins University’s Bloomberg School of Public Health. “We are not going to get past this pandemic unless we have a concerted national approach.”
The new recommendations place high priority on keeping schools open, from kindergarten through 12th grade, saying schools should be both “the last settings to close” and “the first to reopen” because of the critical role they play in providing meals and support services to children. Closures take a disproportionate toll on low-income families, the agency noted.
Officials warned that eating at indoor restaurants was one of the “particularly high-risk scenarios” because diners had to remove their masks. The C.D.C. urged communities to require face coverings on mass transit, something Mr. Biden also has endorsed, and to expand routine screening to identify asymptomatic individuals, who are responsible for about 50 percent of transmissions.
Failure to implement the preventive measures will lead to continued spread of the virus and more unnecessary deaths, said Margaret A. Honein, the first author of the C.D.C. report.
She emphasized that Americans could take many important steps on their own: wearing masks, physically distancing from others, limiting their contacts and avoiding nonessential visits to indoor spaces.
“We want to make sure every person is aware that it’s within their power to take this critical step: Wear a face mask and prevent transmission, and maintain physical distance from others,” said Dr. Honein, a member of the agency’s Covid-19 emergency response team.
Scientific evidence that masks can both prevent an infected individual from spreading the disease and protect the user from infection is “compelling,” she added. “Clearly, not everyone is hearing how important that is,” she said. “It’s an action everyone can take to protect each other.”
Americans also should avoid indoor spaces outside the home, as well as crowded outdoor spaces, the C.D.C. said. That includes restaurants and could also apply to some with outdoor dining: The report suggests switching to takeout food service instead.
Americans should be tested if exposed to the virus and should cooperate with contact tracers if infected, the agency said. They should stay home and postpone travel, air out and ventilate rooms, wash hands frequently and get vaccines as they become available.
Exercise should be done outdoors, with a mask and social distancing, the agency said. Working remotely should be encouraged, and social gatherings should be limited.
In a shift, the C.D.C. also urged states and local jurisdictions to encourage and enforce these behaviors, including mandating the wearing of masks in public spaces and on public transportation.
The Trump administration in September blocked a C.D.C. order that would have required passengers to wear masks on planes, buses and subway trains and in transit hubs. Officials in some states continue to resist mask mandates in public spaces. In Florida, which has reported over a million Covid-19 cases, Gov. Ron DeSantis reiterated his opposition to mask mandates earlier this week.
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The C.D.C. urged officials to limit the use of high-risk nonessential indoor spaces, to erect physical barriers and visual reminders underscoring the need social distancing, and to begin planning now for the distribution and administration of vaccines.
The agency is also pushing for increased testing of essential workers who come into contact with the public and people who are otherwise at high risk.
Even with mass vaccinations apparently imminent, Dr. Honein emphasized the need to implement such measures. “We are seeing that light at the end of the tunnel, but need time to get to that,” she said.
Dr. Nuzzo, of Johns Hopkins, and other experts praised the agency’s new emphasis on prioritizing schools over venues like restaurants and bars, a recommendation echoed by Mr. Biden and his advisers.
The C.D.C.’s previous guidance, issued over the summer and doctored by the White House, also pushed for schools to reopen but was not balanced by a scientific assessment of the accompanying risks, Dr. Nuzzo said, adding, “It felt more like a treatise rather than an analysis.”
Having all 10 measures in one document is helpful and underscores the message that no one strategy can hinder the spread of the virus, experts said. But the document was thin on some details, said Dr. Nahid Bhadelia, medical director of the special pathogens unit at Boston Medical Center.
Dr. Bhadelia was struck by the suggestion that there might be a coordinated program to hand out masks to people. “I haven’t seen that before, particularly for those who are at high risk,” she said. But the C.D.C. did not specify whether states or employers should provide the masks, she noted.
The new guidance also emphasized the importance of improving ventilation in indoor spaces, where airborne virus is a threat. But the agency could have detailed best practices to minimize confusion, Dr. Bhadelia said.
She cited fully enclosed outdoor dining “cabins” as an example of the misguided solutions that can result from unclear guidance.
The agency also did not clarify what the triggers should be for restaurants or schools to shut down or which groups were recommended for increased testing because of their greater interactions with other people. “I would have loved to see a little bit more detail,” Dr. Bhadelia said.