According to a new study, covid-19 infections in the United States could have been four times the number of reported cases, with 1 in 7 U.S. residents infected in mid-November.
As of November 15, approximately 10.8 million cases of Covid-19 were reported at U.S. Centers for Disease Control and Prevention, but the study suggests that the actual number of infections was closer to 46, 9 million.
The study also suggests that approximately 35% of deaths from Covid-19 may not be reported.
“Reported cases of Covid-19 do not represent the full burden of SARS-CoV-2 disease,” the researchers wrote in the study, published in the medical journal JAMA Network Open on Tuesday.
The researchers tested randomly selected blood samples to detect the presence of Covid-19 antibodies in a series of surveys conducted in 10 states as well as in one country. They obtained estimates of the number of infections, hospitalizations, and deaths in the United States as of November 15, comparing the prevalence of antibodies in the samples with the number of reported cases to adjust for subreporting.
According to the researchers, the differences between the number of reported infections and the estimated number of infections decreased over time, suggesting more widespread access to testing in recent months.
The data from this study may be useful in monitoring progress toward herd immunity, as infections continue to increase, but much remains to be done.
“Even after adjusting for the lack of reports, a substantial difference remains between the estimated proportion of the infected population and the proportion of infected people needed to achieve herd immunity,” the researchers wrote.