According to a new study, Covid-19 infections in the United States were possibly four times higher than the number of reported cases, with 1 in 7 US residents being infected in mid-November.
On Nov. 15, about 10.8 million reported cases of Covid-19 were reported to the U.S. Centers for Disease Control and Prevention, but the study suggests the actual number of infections was closer to 46.9 million.
The study also suggests that about 35% of Covid-19 deaths may go unreported.
“The reported cases of Covid-19 do not represent the full disease burden of SARS-CoV-2,” the researchers wrote in the study, which was 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 studies conducted in 10 states, as well as one nationwide. They derived estimates for the number of infections, hospitalizations, and deaths in the US on Nov. 15 by comparing the prevalence of antibodies in the samples to the number of reported cases to correct for underreporting.
The gap between the number of reported infections and the estimated number of infections narrowed over time, suggesting that there will be wider access to testing in later months, the researchers said.
Data from this study may be helpful in tracking progress toward herd immunity as infections continue to increase, but there is still a long way to go.
“Even after adjusting for under-reporting, a significant gap remains between the estimated proportion of the population infected and the proportion infected to achieve herd immunity,” the researchers wrote.