Did Donald Trump Put Joe Biden at Risk of Catching COVID at Presidential Debate?

President Donald Trump has revealed that he has tested positive for the coronavirus, days after the first 2020 election debate with Democratic nominee Joe Biden. Trump's diagnosis prompts questions over whether he may have passed the virus on to his opponent on Tuesday. But experts told Newsweek that while it is possible that Trump infected Biden, many factors are at play.

Trump tweeted on Friday that he and the first lady had tested positive for the coronavirus and would start their isolation and recovery process immediately. In a statement, Trump's physician Sean Conley said both were well, and planned to stay at the White House. He did not state whether the two had shown symptoms.

It is not clear when or from whom the president caught the virus. Hours before revealing his diagnosis, Trump tweeted that he and the first lady were quarantining after Hope Hicks, one of his most senior advisors, tested positive for the coronavirus. Hicks was onboard Air Force One when the president and the first lady traveled to Ohio for Tuesday's debate.

Owing to the ages of the candidates—the president aged 74 and former Vice President Biden 77—both are at risk of serious complications from the coronavirus. The chance of the 50-year-old first lady developing severe COVID-19—the disease caused by the novel coronavirus—is lower when compared with Biden and Trump.

If the president had the virus during Tuesday's debate, it is possible he could have passed it on to Biden, Andrew Preston, an expert in microbial pathogenesis at the University of Bath in the U.K. told Newsweek, adding "but it's hard to quantify." The fact neither were wearing masks slightly increased the chances, for instance, academics told Newsweek.

One of the issues with assessing the risk is the uncertainty around whether the president has symptoms, and if he does when they started, experts said. It is generally accepted that people can be infectious a day or two before developing symptoms.

Dr. Julian Tang, honorary associate professor of respiratory sciences at the University of Leicester, U.K., told Newsweek the incubation period for COVID-19 is around five days. During this period a person could test negative for the virus. He gave the example of an individual being exposed on a Friday, testing negative the next Monday, and then positive the following Friday.

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President Donald Trump speaks during the first presidential debate against former Vice President and Democratic presidential nominee Joe Biden at the Health Education Campus of Case Western Reserve University in Cleveland, Ohio, on September 29, 2020. Trump has since tested positive for the coronavirus. Morry Gash-Pool/Getty Images

The likelihood of passing the virus on is less clear but "certainly possible" for those who test positive but don't show symptoms, Paul Hunter professor in medicine University of East Anglia's Norwich School of Medicine in the U.K., told Newsweek. This is known as being asymptomatic.

"The problem with asymptomatic positives is you never know when they got infected," said Hunter. "Once positive you can remain so for several weeks and for much of that time you may not actually be infectious."

Another consideration is the level of social distancing at the debate, and their behavior. The pair's podiums were positioned relatively far apart, but they were speaking in loud voices, which is known to emit virus into the air, Preston told Newsweek. Also, the debate lasted 90 minutes, and was therefore well over the 15 minute threshold for being considered a close contact, he said.

There have been some reports of the virus circulating between people a few meters apart, such as in a small restaurant in China, Daniel Davis, professor of immunology at the University of Manchester, U.K. told Newsweek. "But the auditorium for the Presidential debate looked large and spacious which makes this very unlikely here," he said.

Davis said it is "very unlikely" Trump passed the coronavirus to Biden. As well as not shaking hands, they entered from opposite sides of the stage.

"Fortunately their obvious animosity towards each other means there is a little chance of a handshake, let alone an embrace between the two of them," Preston said.

Hicks may have posed a greater risk to others than the president if it was the case that she did not wear a mask at the debate venue, as the event was within the 48 hour period before Hope developed symptoms, according to Preston.

William Keevil, professor of environmental healthcare at the U.K.'s University of Southampton, told Newsweek the level of air circulation in the venue is also a "very important" factor when it comes to the potential for spread. "HEPA filtration used on aircraft is the best available system right now but not used frequently in standard buildings," he said.