A team of 39 healthcare researchers has just published a study in JAMA Internal Medicine online that finds that the true number of coronavirus cases in the U.S. could be anywhere from six to 24 times higher than the confirmed number of cases, depending on location, according to a large federal study that relied on data from 10 U.S. cities and states. The study, published on July 21 in JAMA Internal Medicine, made use of serological tests — blood screens that search for antibodies to the virus and that determine whether someone was previously infected, rather than diagnostic tests, which detect those who are currently infected.
The article, “Seroprevalence of Antibodies to SARS-CoV-2 in 10 Sites in the United States, March 23-May 12, 2020,” was written by Fiona P. Havers,, M.D., M.H.S., and 38 other healthcare researchers. In their article, the researchers noted that “The presence of antibodies to SARS-CoV-2 spike protein was estimated using an enzyme-linked immunosorbent assay, and estimates were standardized to the site populations by age and sex. Estimates were adjusted for test performance characteristics (96.0% sensitivity and 99.3 percent specificity). The number of infections in each site was estimated by extrapolating seroprevalence to site populations; estimated infections were compared with the number of reported coronavirus disease 2019 (COVID-19) cases as of last specimen collection date.”
The authors found that “Serum samples were tested from 16 025 persons, 8853 (55.2%) of whom were women; 1205 (7.5 percent) were 18 years or younger and 5845 (36.2 percent) were 65 years or older. Most specimens from each site had no evidence of antibodies to SARS-CoV-2. Adjusted estimates of the proportion of persons seroreactive to the SARS-CoV-2 spike protein antibodies ranged from 1.0% in the San Francisco Bay area (collected April 23-27) to 6.9% of persons in New York City (collected March 23-April 1). The estimated number of infections ranged from 6 to 24 times the number of reported cases; for 7 sites (Connecticut, Florida, Louisiana, Missouri, New York City metro area, Utah, and western Washington State), an estimated greater than 10 times more SARS-CoV-2 infections occurred than the number of reported cases.”
Importantly, they assert that, “During March to early May 2020, most persons in 10 diverse geographic sites in the US had not been infected with SARS-CoV-2 virus. The estimated number of infections, however, was much greater than the number of reported cases in all sites. The findings may reflect the number of persons who had mild or no illness or who did not seek medical care or undergo testing but who still may have contributed to ongoing virus transmission in the population.”
And in closing their article, the researchers write that, “In conclusion, the seroprevalence estimates we report suggest that at the time of specimen collection from March to early May 2020, a large majority of persons in 10 diverse geographic sites in the US had not been infected with SARSCoV-2. The estimated number of infections, however, was much greater than the number of reported cases in all sites. This finding may reflect persons who had mild or no illness or who did not seek medical care or undergo testing but who still may have contributed to ongoing virus transmission in the population. Because persons often do not know if they are infected with SARS-CoV-2, the public should continue to take steps to help prevent the spread of COVID-19, such as wearing cloth face coverings when outside the home, remaining six feet apart from other people, washing hands frequently, and staying home when sick.”