Covid-19 infections in the United States may have been four times the number of reported cases, with 1 in 7 U.S. residents infected in mid-November, according to a new study.
As of November 15, around 10.8 million reported cases of Covid-19 have been reported to the United States Centers for Disease Control and Prevention, but the study suggests the actual number of infections was closer to 46.9 millions.
The study also suggests that around 35% of deaths linked to Covid-19 may go unreported.
“The reported cases of Covid-19 do not represent the total disease burden of SARS-CoV-2,” the researchers wrote in the study published Tuesday in the medical journal JAMA Network Open.
Researchers tested randomly selected blood samples for the presence of Covid-19 antibodies in a series of surveys conducted in 10 states, as well as in one nationwide. They derived estimates of the number of infections, hospitalizations and deaths in the United States as of November 15 by comparing the prevalence of antibodies in the samples to the number of reported cases to correct for underreporting.
The discrepancies between the number of reported infections and the estimated number of infections narrowed over time, suggesting more widespread access to testing in the following months, the researchers said.
The data from this study may be useful in tracking progress towards herd immunity as infections continue to rise, but there is still a long way to go.
“Even after adjusting for underreporting, a substantial gap remains between the estimated proportion of the infected population and the proportion infected needed to achieve herd immunity,” the researchers wrote.