Trump Infected: What Do We Know and Don’t We Know

What happens if he becomes seriously ill?

For the moment, Mr. Trump is said to remain well enough to discharge his duties. If the illness were to become worse, the president under the 25th Amendment could temporarily transfer his powers to Mr. Pence with the transmission of letters to the speaker of the House and president pro tempore of the Senate and then reclaim them once he recovers.

Since the amendment was ratified in 1967, presidents have done so only three times. In 1985, President Ronald Reagan underwent a colonoscopy and briefly turned over power to Vice President George Bush, although he did not explicitly cite the amendment in doing so. President George W. Bush did invoke the amendment twice in temporarily turning over power to Vice President Dick Cheney during colonoscopies in 2002 and 2007.

Who else is infected?

Hope Hicks, one of the president’s closest advisers, tested positive on Thursday, prompting the concern for the president. Ronna McDaniel, the Republican National Committee chairwoman who was with the president last Friday, has also tested positive. Mr. Trump, who almost never wears a face mask, has been in proximity to a number of White House officials, Secret Service agents, military aides and others who are now getting tested.

In addition to Mr. Pence and his wife Karen Pence and Mr. Meadows, those who have tested negative so far are Secretary of State Mike Pompeo; Treasury Secretary Steven T. Mnuchin; Ivanka Trump and her husband, Jared Kushner, both of them senior advisers to the president; Barron Trump, the president’s youngest son; Dan Scavino, the president’s deputy chief of staff; Alex Azar II, the secretary of health and human services; and Judge Amy Coney Barrett, the president’s nominee for the Supreme Court.

It can take several days after exposure for the virus to reach levels that are detectable by a test. People show symptoms on average around five days after exposure, but as late as 14 days.

How did he get it?

Much attention has focused on Ms. Hicks because her condition set off alarms at the White House, but it is not at all clear how the president was infected. He has been in crowded settings repeatedly over the last week and it is possible he infected Ms. Hicks rather than the other way around. The administration said it has started tracing their contacts with people who were near both of them.

Mr. Meadows said the president’s entourage learned that Ms. Hicks’s test had come back positive on Thursday afternoon just as they were taking off on Marine One heading to New Jersey for the fund-raising event. He did not explain why Mr. Trump proceeded with the trip. At the event at Bedminster, Mr. Trump, who was not wearing a mask, addressed hundreds of supporters both outdoors and indoors.