On Jan. 21, 2020, the first official coronavirus infection was documented in Washington state. The infected person had recently visited Wuhan, China, and had come home to the U.S. with the infection.

But scientists have long thought the novel coronavirus had been hitting the United States for weeks before then. And now, a new study has confirmed that seven people in five states may have been infected long before that first official diagnosed case in their states.

  • The study suggests, for example, that the novel coronavirus may have been circulating in Illinois on Dec. 24, 2019. The first case in that state was confirmed one month later.
  • The study analyzed blood tests from people who were diagnosed with COVID-19 to see how soon their antibodies developed.
  • The study reviewed blood samples donated from Illinois, Wisconsin, Pennsylvania, Mississippi and Massachusetts between Jan. 2, 2020, and March 18, 2020.
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The researchers found 147 samples that might have had COVID-19 antibodies. That number was slashed down to nine after further analysis.

  • Seven of those nine people donated their blood before their state’s first diagnosed COVID-19 case, indicating the virus might have been spreading beforehand.

But, according to The New York Times, experts see the study as slightly flawed because the study doesn’t factor in the idea that the antibodies were developed from the common cold and not the novel coronavirus. And the study doesn’t include travel information from those seven patients, either.

  • “This is an interesting paper because it raises the idea that everyone thinks is true, that there were infections that were going undiagnosed,” Scott Hensley, an immunologist at the University of Pennsylvania, told The New York Times.
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This isn’t the first time researchers suggested the novel coronavirus might have been spreading before official cases were diagnosed. For example, a study published in the journal Clinical Infectious Diseases in December 2020 found that the novel coronavirus might have been infecting people in December 2019.

  • “SARS-CoV-2 infections may have been present in the U.S. in December 2019, earlier than previously recognized,” the authors said.

The first reports of a mysterious norovirus spreading through China came out in December 2019. I first wrote about it in early January when health officials said the virus couldn’t spread between humans. Clearly, that isn’t the case, which means the virus could have been spreading before officials knew that the virus could spread so quickly.