At least seven people in five U.S. states were infected with the novel coronavirus weeks before the states reported their first cases, a large new government study showed, pointing to the presence of the virus in the country as early as December 2019.
Participants who reported antibodies against SARS-CoV-2 were likely exposed to the virus at least several weeks before their sample was taken as the antibodies do not appear until about two weeks of infection, the researchers said.
The samples came from Illinois, Massachusetts, Mississippi, Pennsylvania and Wisconsin, and were part of a study of more than 24,000 samples taken for a National Institutes of Health research program between Jan. 2 and March 18, 2020.
Of the seven samples, three were from Illinois, where the first confirmed coronavirus case was reported on Jan. 24, while the remaining four states had one case each. Samples from participants in Illinois were collected on Jan. 7 and Massachusetts on Jan. 8.
The data suggests the virus was in the U.S. states far from the initial hotspots and areas that were considered its points of entry into the country, the study said.
"Data suggest that more rapid and widespread implementation of testing could have allowed us to better realize the spread might have been worse than initially thought, perhaps influencing our level of response," said Micheal Breen, director of infectious diseases and ophthalmology at GlobalData.
The data backs a Centers for Disease Control and Prevention study that suggested the virus may have been circulating in the United States well before the first COVID-19 case was diagnosed on Jan. 19, 2020.
"This study allows us to uncover more information about the beginning of the U.S. epidemic," said Josh Denny, a co-author of the study that was published in the journal Clinical Infectious Diseases.
The United States has so far reported 33.6 million cases, according to a Reuters tally.