President Donald Trump announced in a tweet early Friday morning that he and first lady Melania Trump tested positive for the coronavirus, leading to a slew of questions in the medical community about when, where and how he could have contracted it.
The diagnosis has come as a surprise to some public health experts, given the steps that the White House took to keep the president and his inner circle safe, including regular testing and access to doctors. Press secretary Kayleigh McEnany previously described the president as the "most tested man in America."
As former U.S. Food and Drug Administration commissioner Dr. Scott Gottlieb noted this morning on CNBC: "They created a bubble around the president, and yet he still became vulnerable."
So how did it happen? We asked public health experts and doctors for their take on the timeline of when the president could have been exposed, how long he might experience symptoms and where we go from here.
At this stage, it's all speculation. It's extremely challenging, given the limited data available, to make any hard and fast conclusions. As public health experts explain, it depends on how frequently the president was tested, the type of test he received and the timeline around when he started experiencing symptoms.
There are also still some unknowns about the "early time course" of the disease, said Carl Bergstrom, a biologist and professor at the University of Washington. So even once this information becomes clearer, it may still be a challenge to map out exactly when Trump was exposed.
Of course, there are a few theories that have been thrown out there.
Chief among them is that the president was exposed during the Supreme Court nominee announcement at the White House on Saturday. According to news reports, Notre Dame University President the Rev. John Jenkins, who was in attendance, later tested positive for Covid-19. Jenkins apologized earlier this week to the campus community for not wearing a mask or socially distancing at the event. Moreover, many of the guests, including top Trump administration officials, were photographed without masks.
Another potential clue is that Hope Hicks, a close advisor to the president who traveled with him on board Air Force One several times this week, has also tested positive. But Dr. Megan Ranney, an emergency medicine physician and an associate professor at Brown University, said she doesn't think it's likely that there was a transmission chain through Hicks, given that Hicks tested positive just hours before the president. "It makes far more sense they were exposed to a common vector, but really it's impossible to know."
Again, there are no clear answers at this stage, public health experts stress.
"I suspect the president could have been infected anytime in the past week," said Dr. Jeremy Faust, an attending physician in the Brigham and Women's Hospital Department of Emergency Medicine. "This virus is really hard to track."
The results may be affected by the timing of the test. If the president was tested on the day he was infected, the result would likely come back negative. That's because there might not be enough viral particles in the nose or saliva.
Often, it takes a few days after a person is initially infected — or after they develop symptoms — to get a positive result. Both Trump and the first lady have said that they're now experiencing mild symptoms, but it's unclear when that started.
"It's usually about 48 hours, although there are cases where people were exposed to the virus and more quickly converted to a positive," said Faust.
In the 48 hours before he tested positive and potentially could have been contagious, the president traveled to Ohio, Minnesota and New Jersey, while accompanied by staff who did not wear masks.
During those events, he may have also been in close contact with supporters who did not wear masks.
On Wednesday, he traveled to a rally in Minnesota, where Hicks started to first experience symptoms. As The New York Times has reported, Trump fell asleep on Air Force One on his way back, at which point it became clear that something might be up. Several staffers started wearing masks by Thursday.
Democratic nominee Joe Biden announced Friday afternoon that he's now tested negative for the coronavirus, after standing in proximity to the president for about two hours at the debate Tuesday night.
Still, that doesn't mean Biden is in the clear.
"If you told me you were at a concert and 12 feet away from someone who later tested positive for several hours, I'd tell you to quarantine," said Ranney, the emergency physician. Ranney said Biden will likely be advised by his medical staff to take precautions, particularly if he starts experiencing any symptoms.
"The guidelines are fairly clear," said Faust. "If you have an exposure, you have to quarantine 10 to 14 days, but it's less clear if after 7 to 10 days of negative testing ... you can call it off."
What's not yet known is if Trump could have been infected prior to the debate. The CDC has reported that it's possible for a person infected with Covid-19 to spread the virus for at least a day or two before experiencing any symptoms.
Trump has implied that he was tested before the event. Still, Chris Wallace, who moderated the debate, said in an interview with Fox anchor Bill Hemmer that the president arrived too late in Cleveland on Tuesday to get a Covid-19 test.
"We don't think it's likely you can be contagious with a negative test, although it's always possible that a test was inaccurate," said Faust.
The president tweeted that he and his wife, Melania, will quarantine as they recover. Thus far, both have said that their symptoms are mild, although that could change over time.
On Friday afternoon, White House physician Dr. Sean Conley said Trump was "fatigued but in good spirits" while the first lady had a mild cough and headache.
Trump received a single 8-gram dose of Regeneron's experimental antibody cocktail as "a precautionary measure," Conley said.
Trump left the White House for Walter Reed Military Medical Center on Friday evening. This step was taken "out of an abundance of caution, and at the recommendation of his physician and medical experts," press secretary Kayleigh McEnany said in a statement. The White House said the president will be working from the presidential offices at the medical center.
Conley added that the first family had tested negative for the virus last Friday.
Even if Trump were to test negative in subsequent days, he should still continue to isolate, public health experts note. How long he isolates might depend on the severity of his symptoms. The 74-year-old president has several risk factors that could increase the likelihood that he'll experience severe illness, including his age, gender and weight.
The latest public health guidelines suggest that people with mild to moderate Covid-19 symptoms are infectious for up to 10 days after the onset of symptoms. Those with more severe illness or those who are severely immunocompromised can remain infectious for 20 days.
The CDC recommends those who are able to recover at home should only stop isolating if:
"So really we're looking at a minimum of 10 days," said Ranney.