The coronavirus was likely in the U.S. as early as mid-December 2019, roughly a month before the first COVID-19 case was confirmed, according to research published on Monday.
A study of blood samples from 7,389 routine donations to the American Red Cross between Dec. 13, 2019, and Jan. 17, 2020, found evidence of COVID-19 antibodies in 106 specimens, according to researchers with the Centers for Disease Control and Prevention.
The donations were made in nine states ― California, Connecticut, Iowa, Massachusetts, Michigan, Oregon, Rhode Island, Washington and Wisconsin. Donations with antibodies reactive to SARS-CoV-2, the virus that causes COVID-19, came from all nine.
Despite the timing of these donations, it wasn’t until Jan. 15 that U.S. health officials confirmed what they believed was the country’s first COVID-19 case. This followed China reporting cases of the illness late last year. By March, the World Health Organization declared the outbreak a pandemic.
“These findings suggest that SARS-CoV-2 may have been introduced into the United States prior to January 19, 2020,” researchers stated in their report.
These early cases may not have been detected for a number of reasons, including that patients didn’t seek medical care because their symptoms were mild or nonexistent, the report states.
“For those with symptomatic infections who may have sought medical care before SARS-CoV-2 was known to be circulating in the U.S., clinical samples may not have been collected and therefore respiratory virus testing may not have been performed; even fewer specimens would likely be archived and available for retrospective molecular testing,” the report adds.
Blood donors who had COVID-19 were likely asymptomatic when they donated their blood to the Red Cross since each donor had to be screened for bacterial or viral respiratory infections, including influenza. We now know that the symptoms of those infections are similar to those of COVID-19 patients. If prospective blood donors were not well, they would have been asked to come back another time, researchers said.
Health experts already suspected that the virus arrived in the U.S. weeks to months before it was officially recorded.
Researchers from the University of California, Los Angeles, and the University of Washington reported in September that there had been an unusual increase in patients seeking treatment for respiratory illness beginning the week of Dec. 22 and continuing through to the end of February.
Researchers noted in their report on Monday that they couldn’t determine whether the blood donors’ infections were from community spread or travel.
To offer some idea, however, the researchers referenced a previous unrelated survey of blood donors’ travel. It found that less than 3% of survey respondents reported having traveled outside of the U.S. within 28 days before donating blood. Of that percentage, only 5% said they had traveled to Asia, where the coronavirus is believed to have originated.
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