After a study by researchers from the University of Florida on asymptomatic spread of COVID was published on Dec. 14, some social media posts claimed that COVID is not spread by asymptomatic or presymptomatic carriers. Politifact has since published an article rating these claims as “Mostly False.”
The study, published by the Journal of the American Medical Association, was a meta-analysis of 54 studies with 77,758 total participants. It examined household virus spread and “secondary attack rates,” the amount of spread from an infected person to an uninfected person. The study found that secondary attack rates were higher for symptomatic people than asymptomatic people — an 18% rate for symptomatic people and a 0.7% rate for asymptomatic people.
“Household secondary attack rates were increased from symptomatic index cases (18.0%; 95% CI, 14.2%-22.1%) than from asymptomatic index cases (0.7%; 95% CI, 0%-4.9%), to adult contacts (28.3%; 95% CI, 20.2%-37.1%) than to child contacts (16.8%; 95% CI, 12.3%-21.7%), to spouses (37.8%; 95% CI, 25.8%-50.5%) than to other family contacts (17.8%; 95% CI, 11.7%-24.8%), and in households with 1 contact (41.5%; 95% CI, 31.7%-51.7%) than in households with 3 or more contacts (22.8%; 95% CI, 13.6%-33.5%),” according to the study results.
According to Politifact, the study findings led many, including Jenny Beth Martin, co-founder of the Tea Party Patriots, to claim that there is zero COVID spread from asymptomatic carriers. “University of Florida researchers have found no asymptomatic or presymptomatic spread of COVID,” Martin tweeted. “This could change everything.”
Martin later tweeted, “Clarification: The study found asymptomatic spread to be insignificant or statistically zero in household environments, which continue to be important venues for transmission.”
According to the Politifact article, “There’s consistent evidence that asymptomatic individuals are less likely to spread the virus than symptomatic individuals are. But the paper didn’t find the rate of spread to be zero.”
The article also noted that the study addresses only household spread and not community spread.
“Asymptomatic people going about their lives in the community would encounter many more people than someone stuck at home, meaning they could still infect a sizable number of people,” according to the article.
Furthermore, the study itself notes that there are still few studies on secondary attack rate from asymptomatic and presymptomatic COVID cases, indicating that more research could be necessary to determine the amount of spread.