Researchers, including scientists from the Centers for Disease Control and Prevention (CDC) and the American Red Cross, have found evidence that Covid-19 was present in the U.S. in December 2019, weeks earlier than previously thought and before even the first cases in Wuhan, China, had been publicly identified.
Findings from the study, which tested stored blood samples from between December 2019 and January 2020 for Covid-19 antibodies and were published in the journal Clinical Infectious Diseases, indicated the presence of Covid-19 in several U.S. states “earlier than previously recognized.”
Researchers found positive test results, indicating prior exposure to the virus responsible for Covid-19, in samples from California, Oregon and Washington in mid-December, much earlier than the first official U.S. case on Jan. 19.
Samples from Connecticut, Iowa, Massachusetts, Michigan, Rhode Island, and Wisconsin were also found to test positive for Covid-19 in January, before Covid-19 was believed to be present.
The study’s authors say they will continue to work with the U.S. government and non-government partners to use blood samples to analyze the pandemic, adding that an understanding of how the pandemic progressed from its early stages to the global crisis seen today will help public health officials better allocate resources to prevent illness and death.
While the presence of antibodies in a person’s blood means they have been exposed to the pathogen in the past — in this instance the virus that causes Covid-19 — the kinds of tests used in this study are broader and less specific than would be needed to confirm that without any doubt. It is possible, as the authors themselves acknowledge, that the tests are picking up another kind of antibody that, while similar, is distinct; coronaviruses are a large and relatively common family of virus, including some that can cause the common cold, leaving open the possibility that infection by a non-Covid-19 virus induced the positive test results. The researchers did take steps to minimize these risks, but they are not zero.
Scientists have been quick to question the study’s conclusions on social media, citing these uncertainties. Trevor Bedford, a scientist at Fred Hutch, said, for example, that the study does not necessarily mean the virus was in the U.S. in December, and that the positive results could possibly be explained by the blood donor having recently recovered from a seasonal coronavirus infection, not Covid-19.
What We Don’t Know
The origins of Covid-19 are still largely a mystery, with the virus believed to have crossed over from animals into humans in the later months of 2019. Today, Dec.1 2020, is believed to be the first anniversary of the first identified case from a novel coronavirus that had been circulating in the city of Wuhan, in China. It goes without saying that the search for the virus’ origins is political — some, including U.S. President Donald Trump, are even calling for China to pay reparations for its apparent role in the virus’ emergence — something the World Health Organization is having to grapple with as it tries to get boots on the ground in China. In recent weeks, the Guardian reports that China has been embarking on a blame-shifting propaganda campaign, trying to relocate the virus’ origin outside of China.
Serologic testing of U.S. blood donations to identify SARS-CoV-2-reactive antibodies: December 2019-January 2020 (Clinical Infectious Diseases)