Fauci predicts up to 200,000 U.S. deaths as Trump weighs adjusting coronavirus guidelines. Here is what you should know.

John Fritze | USA TODAY

Show Caption Hide Caption Trump rips 'unappreciative' governors, tells Pence not to call them President Trump told reporters that certain governors are not appreciative enough of his administration's response to the coronavirus pandemic.

WASHINGTON – As President Donald Trump weighs whether to ease social distancing guidelines intended to slow the spread of coronavirus one of his top health advisers predicted Sunday as many as 200,000 Americans could die from the disease.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, projected millions of Americans will contract COVID-19 and between 100,000 and 200,000 people could succumb to it. The Centers for Disease Control and Prevention's worst-case-scenario earlier estimated at least 200,000 could die from the virus this year.

Public health officials reiterated the grim estimates Sunday as the Trump administration weighed whether to extend its 15-day guidance to slow the spread the virus. Trump has said he wants to lift recommendations that Americans work from home and avoid discretionary shopping, but also said he would consider input from health experts.

"Looking at what we're seeing now, I would say between 100,000 and 200,000" deaths, Fauci told CNN’s "State of the Union." "We're going to have millions of cases."

At midday Sunday, the U.S. had recorded about 125,000 coronavirus cases, according to Johns Hopkins University, though the true number is likely much higher. The university had tallied 2,201 deaths, with by far the highest share in New York City.

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Where are things now?

The Centers for Disease Control and Prevention projected a worst-case scenario of 160 million to 210 million cases by December. Under that forecast, 21 million people would need hospitalization and 200,000 to 1.7 million could die by the end of the year. Health officials have cautioned that the models of infection rate vary widely.

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Fauci, who described the estimates as a “moving target,” was among several members of the Trump administration coronavirus effort appearing on Sunday political shows. Whatever the numbers, the experts agreed that the virus continues to pose a major threat, including to states and cities that have not yet had a heavy caseload.

"No state, no metro area will be spared," Deborah Birx, the White House coronavirus response coordinator, told NBC's "Meet the Press." "We are asking every single governor and every single mayor to prepare like New York is preparing now."

It's not yet clear how those warnings square with Trump's desire to "reopen" the nation and restart the economy. Trump has said he hopes many Americans could go back to work by Easter, potentially beginning in some of the least hard-hit parts of the country. But Trump has not said specifically how he came up with that date or why he feels it is realistic.

Another outstanding question is how much of an impact lifting or adjusting the federal guidelines would have. The more stringent and enforceable restrictions have been imposed by state officials in New York, California and elsewhere. An easing of federal guidelines might influence governors in those states, but it wouldn't require a response.

Where the estimates come from

Estimates are based on extrapolation of data, in other words drawing conclusions about what has happened in other areas and applying those to the nation. The predictions depend on the continuation of existing factors, such as rates of transmission, said Ogbonnaya Omenka, an assistant professor and public health specialist at Butler University's College of Pharmacy and Health Sciences.

"But those conditions are liable to change, so you cannot say with utmost certainty that things would unfold as predicted," Omenka told USA TODAY.

Fauci's numbers are "within reason," Omenka said, because a recent survey result applied to the entire U.S. population would put the expected number of cases nationwide at about 8 million. Still, because of shortfalls in testing, the real number of cases is likely to be much higher than current reports show, Omenka said.

What happens next is vital

Trump has repeatedly said he would listen to public health officials before deciding whether to extend or alter the federal guidelines. Fauci indicated that the president did just that over the weekend, backing down from an initial plan to impose a quarantine in New York and other especially hard-hit states in the Northeast.

The president told reporters on Saturday that he was considering a weekslong quarantine for New York and parts of New Jersey and Connecticut. Public health officials are concerned that nonsymptomatic residents of those states may be spreading the virus to other areas as they travel around the country.

But after the idea drew criticism from state officials, including New York Gov. Andrew Cuomo, Trump instead announced a "strong" travel advisory.

"The original proposal was to consider seriously an enforceable quarantine," Fauci told CNN. "After discussions with the president, we made it clear, and he agreed, that it would be much better to do what's called a strong advisory."

Omenka said that the state and federal government must be careful about causing a second wave of infection by reopening public spaces too soon. Public health officials and the president, he said, should be guided by whether rates of transmission slow.

"The peak has to start coming down before we can start to confidently revise strategies," Omenka said. "Just because a jurisdiction overcomes the outbreak does not mean they are entirely safe."

That advice appeared to align with a report Sunday from the American Enterprise Institute written by Scott Gottlieb, former head of the Food and Drug Administration.

The report suggested strict social guidelines remain in place until a state reports a "sustained reduction in cases" for at least two weeks "to guard against the risk that large outbreaks or epidemic spread could reignite once we lift our initial efforts."

Contributing: John Bacon