It's too late to trace infections at the White House Rose Garden ceremony, experts say: 'I bet you we'll never find out'

• President Donald Trump and at least 34 White House staffers and contacts have been infected with the coronavirus following Judge Amy Coney Barrett's nomination ceremony at the White House Rose Garden on September 26.
• The White House accepted the CDC's offer to help with contact tracing on Wednesday, The Washington Post reported.
• Epidemiologists say those efforts may have come too late: People should be tested within two weeks of getting exposed.
• The outbreak has likely "spread beyond the White House at this point," one expert said.

Recent visitors to the White House received a letter from health officials on Thursday. It came with a warning: If they had worked in the White House in the past two weeks, attended the recent Supreme Court announcement ceremony, or had close contact with people who fit that description, they should get tested for the coronavirus. Ideally, they should already be quarantining as well.

The letter, signed by 10 health departments in the Washington, DC, area, expressed concern about a lack of contact tracing following a superspreader event at the White House.

Nearly 200 people gathered in the White House's Rose Garden on September 26 to see President Donald Trump officially nominate Judge Amy Coney Barrett to the Supreme Court. The majority of those attendees didn't wear a mask. Many hugged and shook hands. A smaller group attended an indoor reception following the ceremony, where they again mingled without masks.

At least 34 White House staffers and contacts have since been infected with the coronavirus, according to an internal memo from the Federal Emergency Management Agency. That includes bodyguards, family members, pastors, journalists, GOP senators, and advisors.

Trump tested positive for the virus on October 1. Shortly after, the Centers for Disease Control and Prevention offered to help the White House with contact tracing, The Washington Post reported. The White House initially rejected the invitation, a CDC official told The Post, but finally began cooperating with two CDC epidemiologists on Wednesday.

On Thursday, a senior White House official told The Post that the White House had finished contact tracing related to the president's infection. But White House staffers and administration officials said that many people with potential exposure hadn't heard from health officials yet.

Epidemiologists say attempts to identify infections at the Rose Garden ceremony may have come too late.

"It's hard enough to do a normal contact trace. I'm in the middle of doing one right now, and it's hard enough to do when people are cooperative and you're doing it by the book," Yvonne Maldonado, an epidemiology professor at Stanford University, told Business Insider. "But when you have a random email out to a bunch of people and some people might respond, some won't, it's going to be really hard to know."

The administration's delayed efforts could forever obscure the true scale of the outbreak, she added.

"I bet you we'll never find out because you're assuming that everybody got tested whether they had symptoms or not and that never happens," Maldonado said. "You'd need to test everybody over two-week period."

At the very least, experts say, the list of infected individuals is probably longer than what has been confirmed thus far.

"These are people with extremely busy jobs and a lot of people that they come in contact with every day," Rachel Graham, an assistant epidemiology professor at The University of North Carolina at Chapel Hill, told Business Insider. "It's reasonable to assume that it's also spread beyond the White House at this point."

Early contact tracing could have contained the outbreak

Epidemiologists rely on a three-step strategy to contain the virus: test, trace, isolate. Those steps must go in order. If any one of them fails, the whole system falls apart.

That's why testing a person right after they've been infected is so important. The quicker epidemiologists can identify cases, the better chance they have of getting people to isolate before infecting others. But it's not enough to test each person once.

"If you're negative on day one post-exposure, that doesn't mean anything," Graham said. "You'd need to be negative on day seven post-exposure for that to start to mean something."

White House Press Secretary Kayleigh McEnany is a prime example: McEnany tested negative for several days following the Rose Garden ceremony. During that time, she continued to brief reporters in person, without wearing a mask. Then her test came back positive on October 5.

Health officials usually advise people to isolate for 14 days from their date of exposure or 10 days after their symptoms start. Two weeks is enough time for the virus to grow to detectable levels inside the body, so people who haven't tested positive by then aren't likely to have been infected. Data also shows that COVID-19 patients stop shedding enough virus to infect others after seven to 10 days of symptoms.

It's not clear how many people who attended the Rose Garden ceremony were tested during that window. But since the event was more than two weeks ago, testing them now probably won't yield many answers.

"Basically all of those people are either infected or not infected by this point," Maldonado said.

It's also unclear how many people have isolated after coming in contact with suspected cases.

"Since we do know for a fact that there are people who have tested positive that have since returned to work too fast, the chances of additional transmission can't be guaranteed against," Graham said.

If everyone at the Rose Garden ceremony was tested and all those who tested positive were quarantined, she added, the White House may have been able to contain the outbreak. But a lack of contact tracing probably allowed infections to ripple into the surrounding community.

"Basically this is how the pandemic started," Maldonado said. "This chain of transmission could just keep going."

Tracking down patient zero

White House officials seem to have abandoned the idea of tracking down patient zero at the Rose Garden ceremony.

"There were a number of guests who have been at the White House who maybe tested negative, but then later tested positive," White House spokesman Brian Morgenstern told reporters on Wednesday. "So, it's sort of an unknowable question as to where it entered the environment. But where do we go from here is trying to mitigate further transmission."

But experts say early contact-tracing efforts would have made it much easier to identify the original source.

For example, at least nine people in the first four rows of the outdoor ceremony have tested positive so far. And at least five confirmed cases went to the indoor reception. That may offer clues about where contact tracers should start.

From there, contact tracers would also consider how long people were interacting with one another. People who went within six feet of someone who tested positive or had contact with an infected person for 15 minutes or more would have the highest risk of getting sick themselves.

Graham said it's more likely that the virus spread indoors, but the size of the Rose Garden ceremony still presented ample opportunities for transmission.

"If you're still crowding a bunch of people into one place, it almost doesn't matter if it's outdoors. You're still producing a large cloud of respiration that can be easily transferred to the person sitting next to you," she said. "So it really is if you're not wearing a mask, if you're not protecting yourself from droplet transmission, you are becoming part of the potential chain of transmission."

But identifying patient zero would prevent contact tracers from having to test every person in the crowd.

"I'm sure they have an idea of who the source is, but we'll never find out probably — or maybe we'll find out after the election," Maldonado said. "Somebody's dying notes will say, 'Oh, you know, we knew who it was.'"