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COVID-19 may have already arrived in the United States in December 2019, before the disease was even identified in China, a new study suggests.
Researchers in the study, from the Centers for Disease Control and Prevention (CDC), analyzed more than 7,000 blood donations collected by the American Red Cross in nine states between December 13, 2019 and January 17, 2020.
Of these, 106 samples tested positive for antibodies to SARS-CoV-2, the virus that causes COVID-19.
The findings suggest that “SARS-CoV-2 infections may have been present in the United States in December 2019, earlier than previously recognized,” the authors wrote in their paper, published Monday (November 30) in the journal Clinical infectious diseases.
Officials in China first reported a group of mysterious pneumonia cases in Wuhan, which were reported to have been caused by COVID-19, on December 31, 2019.
In the United States, the first confirmed case of COVID-19 was reported on January 20, 2020 in a Washington state resident who had recently traveled to China.
But there have been indications that the virus was circulating earlier than recognized. A case of COVID-19 in China has been reportedly traced back to November 17, 2019, Live Science previously reported.
In France, retrospective testing of samples from hospitalized patients revealed an infected patient in late December 2019. And researchers found SARS-CoV-2 antibodies in blood samples collected in Italy in September, Live Science previously reported. com.
In the new study, of the 106 samples that tested positive for SARS-CoV-2 antibodies, 39 were collected from California, Oregon, and Washington between December 13-16, 2019; and 67 were collected from Connecticut, Iowa, Massachusetts, Michigan, Rhode Island, and Wisconsin between December 30, 2019 and January 17, 2020.
Positive antibody tests suggest a previous COVID-19 infection, but they cannot prove that a person has been infected. There is a possibility that antibodies to other coronaviruses may “cross-react” to give a positive result.
But when the researchers ran further tests to account for that cross-reactivity, they found that 84 of the 90 samples tested had antibodies specific to SARS-CoV-2.
The authors also used a highly accurate test for SARS-CoV-2 antibodies. But even very accurate tests still produce a small number of false positive results.
However, the number of positive results in the new study was higher than what would be expected from false positives alone, the researchers wrote.
Overall, these results “make it very unlikely that all samples will be reactive [positive results] represent false positives, “concluded the authors.
In other words, at least some of these positives as of December 2019 and early January 2020 were likely due to previous COVID-19 infections.
However, even though the authors tried to measure antibodies specific to SARS-CoV-2, “cross-reactivity with other coronaviruses” cannot be ruled out, said Dr. George Rutherford, professor of epidemiology and biostatistics at the University of California, San Francisco, he told Live Science.
And even if these were true COVID-19 infections, the study cannot determine where the participants acquired the infection – it is possible that some blood donors in the study recently traveled to China and were infected there, Rutherford noted. . (The current study had no information on whether and where the donors had traveled.)
Also, due to the limitations of the study, the results cannot reveal how much the virus was circulating at the time.
To confirm the findings, human tissue, saliva, or blood samples from that period should be tested for traces of genetic material from the SARS-CoV-2 virus, the authors said.
Rutherford added that donors could be contacted in future studies, which could provide information on whether they have traveled or experienced symptoms similar to those of COVID-19.
This article was originally published by Live Science. Read the original article here.
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