—During March to early May 2020, most individuals in the United States had not been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), although the estimated number of infections seems to have been much higher than the number of reported cases, according to a study published online July 21 in JAMA Internal Medicine.
Fiona P. Havers, M.D., from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues estimated the prevalence of SARS-CoV-2 antibodies in convenience samples from 16,025 persons from 10 geographic sites across the United States. Serum was collected from March 23 through May 12, 2020, for routine clinical testing.
The researchers found no evidence of antibodies to SARS-CoV-2 for most specimens from each site. There was variation seen in the adjusted estimates of the proportion of persons seroreactive to the SARS-CoV-2 spike protein antibodies, from 1.0 percent in the San Francisco Bay area to 6.9 percent among persons in New York City. The estimated number of infections was six to 24 times higher than the number of reported cases; for seven sites, more than 10 times more SARS-CoV-2 infections occurred compared with the number of reported cases.
“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 6 feet apart from other people, washing hands frequently, and staying home when sick,” the authors write.