Dr. Anthony Fauci, the nation’s leading infectious disease expert, and Dr. Deborah Birx, who is coordinating the White House’s response, encouraged people to adhere to distancing guidelines, noting that more than 2.2 million Americans could have died if nothing had been done.

As of this morning, there have been at least 3,900 virus-related deaths in the U.S. Here are the latest updates and maps of the pandemic.

We also have a daily tracker showing the virus’s trajectory by country and U.S. state as well as a look at where Americans have been urged to stay home.

In other developments:

As many as 25 percent of people infected with the virus may not show symptoms, a number that is leading the C.D.C. to consider broadening its guidelines on who should wear masks. (We have a guide to making your own.)

Governors from across the political spectrum are challenging the Trump administration’s assertion that the U.S. is well-prepared to test people and care for the sickest patients. Asked on Tuesday whether President Trump’s suggestion that a lack of diagnostic kits was no longer a problem, Gov. Larry Hogan, Republican of Maryland, said, “That’s just not true.”

Mayor Bill de Blasio said medical personnel from around the country were arriving to help shore up New York’s health care system. He warned that the city expected a huge increase in cases next week. Here are the latest updates from our Metro desk.

Places in Asia that seemed to have brought the epidemic under control are tightening restrictions, fearing a wave of new infections imported from elsewhere.

Mr. Trump has been reluctant to use the full force of a wartime production law to respond to the pandemic. It has already been invoked hundreds of thousands of times during his presidency.

Support from independents and some Democrats has driven Mr. Trump’s approval rating to 49 percent, equal to the best of his presidency.

News analysis: “A crisis that Mr. Trump had repeatedly asserted was ‘under control’ and hoped would ‘miraculously’ disappear has come to consume his presidency,” our chief White House correspondent writes.

The details: We’ve updated the expert guidance we’ve compiled on several subjects, including health, money and travel.