Trump's refusal to wear a mask may have led him to be exposed to more coronavirus particles — raising his risk of severe infection

• Trump's failure to consistently wear a face mask raises the risk that he was exposed to a higher dose of the coronavirus.
• If Trump wasn't wearing a mask when infected, he would probably have taken in a larger amount of virus particles than he would have had he worn protective equipment.
• Some research suggests that being exposed to higher doses of virus can lead to more virus in the body, which could cause more severe illness.

President Donald Trump's habit of not wearing a mask may have both exposed him to the coronavirus in the first place and raised his risk of developing a more severe infection.

That's because emerging research suggests masks could help reduce viral inoculum: the dose of virus that people ingest or inhale. That, consequently, could reduce the amount of virus replicating inside a patient — their viral load.

Higher viral loads, some research suggests, could lead to worse infection outcomes.

"I would be concerned that [Trump] may have been exposed to higher viral inoculum, just not having that mask on," Monica Gandhi, an infectious-disease expert and professor of medicine at the University of California, San Francisco, told Business Insider, adding, "that could predispose you to more severe illness."

On Friday, the New York Times reported, the president had a low-grade fever, cough, and nasal congestion in addition to the fatigue that the White House disclosed. Trump was admitted to Walter Reed Medical Center Friday evening, after getting an injection of Regeneron's experimental antibody drug, which is not yet FDA-authorized.

Trump has a mask aversion

The Centers for Disease Control and Prevention has advised people to wear masks in public since April 3, by which point overwhelming evidence showed that face coverings reduce transmission, thereby saving lives. But that same day, Trump downplayed the recommendation.

"I don't think I'm going to be doing it," he said at a press briefing.

Trump did not begin encouraging Americans to wear masks until the summer, and was not photographed wearing one himself until July. Since then, he has regularly made mask-free appearances, including at campaign rallies.

During Trump's preparations for Tuesday's debate, nobody in the room with him was masked, former New Jersey Gov. Chris Christie told ABC's "Good Morning America."

On stage on Tuesday, Trump made an effort to distinguish himself from Joe Biden on the question of masks: "When needed, I wear masks. I don't wear masks like him," Trump said.

Even after Trump's diagnosis on Friday, the White House will not start requiring face masks, the Associated Press reported, because wearing a face covering is a "personal choice."

Masks could help prevent more severe illness

Evidence by now clearly shows that face masks and social distancing are associated with declines in coronavirus death rates.

That's in large part because mask-wearing reduces the risk that people get exposed to the coronavirus in the first place. But new research from Wayne State University suggests it might also be because a mask can reduce the quantity of viral particles a person who is exposed takes in, thereby lowering their risk of severe infection.

The study found that the average viral load among patients at the Detroit Medical Center has declined over the course of the pandemic, while at the same time infections have gotten milder.

"All those social measures we were taking and teaching may have something to do with the people coming in with lower and lower amounts of virus," Dr. Pranatharthi Chandrasekar, the study's senior author, told Business Insider. "As they get exposed to people while they're wearing masks, they are probably getting exposed to a smaller quantity of the virus."

It seems logical that if a person is exposed to fewer viral particles, the lower quantity of virus in their system may in turn translate to a lower risk of mortality.

"Studies have been hinting that a lower viral load is occurring over time and that it's linked to lower mortality, but this is the first study to show this systematically," Gandhi said, adding, "a low viral load from swabs likely indicates an ability to control the viral infection better and, therefore, have less severe disease."

But Chandrasekar said more research is needed to draw a definitive link.

Still, these findings might apply to Trump's case. If he wasn't wearing a mask around whoever transmitted the coronavirus to him, he may end up with a higher viral load — and more severe symptoms — than if he had been wearing one.

If Trump contracted the virus from White House advisor Hope Hicks, for example — who tested positive on Thursday after showing COVID-19 symptoms — that could also have doused the president in a large amount of viral particles.

"There is really new data that people who are symptomatic have higher viral loads in their nose and mouth," Gandhi said Friday morning. "So she could have exposed him... to a higher dose."