There’s A Good Chance You Already Had COVID: 1 In 3 Americans Did In 2020, Study Says

As many as 103 million Americans are estimated to have been infected with COVID-19 at the end of 2020, according to a new study released by the Columbia University Mailman School of Public Health.

The study, which was published in the journal Nature, suggests that 31% of the U.S. population had COVID last year but only 22% of infections were reported through public health testing.

The university said it performed the study to “quantify the overall burden and characteristics of COVID-19 in the U.S. during 2020.”

For the study, researchers simulated COVID transmission within and between all 3,142 U.S. counties using population, mobility, and confirmed case data.

Here, there they found that in the upper Midwest and Mississippi valley, more than 60% of the population was estimated to have been infected with the virus by the end of 2020. In Chicago alone, they discovered that 48% of residents had COVID by the end of the year and 52% of Los Angeles residents were infected with the virus by the end of 2020.

Other metropolitan areas also saw high infection rates during the same timeframe, including Miami (42%), New York City (44%), and Phoenix (27%).

Researchers reasoned that the “incomplete picture” was due to “individuals with mild or asymptotic infections, who could still spread the virus, were less likely to be tested.”

“The vast majority of infectious were not accounted for by the number of confirmed cases,” Jeffrey Shaman, professor of environmental health sciences at Columbia University Mailman School of Public Health, said in a statement. “It is these undocumented cases, which are often mild or asymptomatic infectious, that allow the virus to spread quickly through the broader population.”

However, in 2021, researchers suggest that the virus will spread to those that have not yet been infected, and while vaccines will protect against severe disease and fatalities, “new more contagious variants make reinfection and breakthrough infections more likely.”