A growing number of people in and around the White House have tested positive for the coronavirus — including President Donald Trump himself.

The president announced late Thursday night that he and first lady Melania Trump had tested positive for the coronavirus, joining several other high-ranking US government officials who have contracted SARS-CoV-2. Trump went to Walter Reed National Military Medical Center in Bethesda, Maryland, on Friday evening to undergo treatment.

Republican Sens. Mike Lee of Utah and Thom Tillis of North Carolina also announced they tested positive; both attended an event last weekend honoring the nomination of Judge Amy Coney Barrett to the Supreme Court. Several other people, including former senior White House counselor Kellyanne Conway and Trump campaign manager Bill Stepien, also tested positive on Friday after attending the event at the White House. Former New Jersey Gov. Chris Christie announced Saturday morning that he has tested positive.

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Barrett, for her part, was diagnosed with the coronavirus over the summer but has recovered. It is unknown whether she now carries immunity. It is worth noting that beyond the relatively well-known senators, members of the press and White House officials who have tested positive, it’s possible less well-known staff members and security officers could have been infected with the coronavirus.

But it’s not just the one event. On Saturday, Sen. Ron Johnson (R-WI) also announced having tested positive. Johnson was not at the event, but he did attend a lunch with other Republican senators this week.

The White House, in other words, is now a Covid-19 hot spot.

While it’s not clear how the president was exposed, Trump was in regular contact this week with senior counselor Hope Hicks, who tested positive on Thursday afternoon. Hicks had traveled with Trump multiple times this week, including to Tuesday night’s presidential debate in Cleveland, Ohio.

Over the summer, Republican Sens. Rand Paul and Bill Cassidy were diagnosed with Covid-19 but have successfully recovered. The virus has also infected at least 14 House members — nine Republicans and five Democrats — since March. But this is the first time the virus, which has killed more than 208,000 Americans, has spread in such a concentrated manner among White House officials, staffers, and members of the press corps.

As of early Friday afternoon, Vice President Mike Pence and his wife Karen have both tested negative, as have Democratic nominee Joe Biden and his wife Jill. Secretary of State Mike Pompeo and Director of National Intelligence John Ratcliffe tested negative as well.

Trump and his staff have been traveling to campaign events for several weeks. Just in the last week, the president has held rallies in Florida, Virginia, Pennsylvania, and Minnesota, in addition to the debate in Ohio. Bill Stepien, Trump’s campaign manager, tested positive Friday night.

Sen. Marsha Blackburn, a Republican from Tennessee, flew with Trump to the debate, and on Friday said she was getting tested and isolating “out of an abundance of caution.” Later that day, she said she had tested negative, as did Sen. Kelly Loeffler (R-GA).

One way to mitigate the outbreak from the event is to undergo a major contact tracing operation, though it is unclear if the White House is doing so. As Vox’s Dylan Scott explained, the only way to figure out the full extent of the outbreak is contact tracing: “identifying who has been in close contact with the president since he became contagious, and asking them to quarantine to prevent Covid-19 from spreading to others, and to get tested themselves.”

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The Trump campaign announced in a statement Friday that he and his family are suspending in-person events. Pence’s campaign travel will continue and he plans to participate in the vice presidential debate against Democratic vice presidential nominee Sen. Kamala Harris on Wednesday.

Here’s what we know about who has tested positive — and negative — for SARS-CoV-2 so far.

The list of people who have tested positive for the coronavirus

A brief list of key politicians and officials who have tested negative

Given the level of uncertainty created by this news, Vox has compiled a list of key administration figures who help run the country, key lawmakers who have been in contact with the president, and key Democrats in the 2020 election cycle who have recently gotten negative test results for the virus.

While it could take several days for an individual who has contracted the virus to test positive, these are the initial negative tests. As of 4:15 pm Saturday, here’s the list: