Study: Nearly 17 million COVID cases undetected in U.S. by July of last year

A study published this week reports that serological data points to the conclusion that SARS-Cov-2 was spreading much more widely through the U.S. during the early months of the pandemic than was previously thought, with tens of millions of cases going undetected even as late as mid-July of last year.

The study, published in Science Translational Medicine, looked at blood samples collected between May and July of last year, measuring their seropositivity for antibodies to the SARS-Cov-2 virus. 

"These data indicate that there were 4.8 undiagnosed SARS-CoV-2 infections for every diagnosed case of COVID-19," the scientists state, “and an estimated 16.8 million infections were undiagnosed by mid-July 2020 in the United States.”

By mid-July of last year, confirmed cases in the U.S. stood at about 2.3 million, suggesting that the virus may have spread more easily and rapidly than even the more dire predictions estimated at that time.

"Our data suggest a larger spread of the COVD-19 pandemic in the United States during the first six months than originally thought," the scientists write.