Findings released by the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) suggest that SARS-CoV-2 disease was present in the U.S. much earlier than thought.
It is now officially accepted that the onset of the Covid-19 pandemic occurred in Wuhan, China, in late 2019. In early 2020, the Chinese informed the World Health Organization (WHO) that they were dealing with an unexplained viral pneumonia outbreak, did not know the nature of the first cases, and recorded the first cases in November/December 2019. As for the United States, the official version is that the first case was reported on January 19 and it was a person who returned from a trip to China. But according to new research, specifically antibodies in blood samples taken in December, Covid-19 most likely found its way to the U.S. much earlier. How much earlier? Weeks, if not months!
The first study was conducted by the National Institutes of Health, looking at blood samples collected as part of a long-term observational study called All of Us. Researchers analyzed samples collected from 24,000 people between January and March 2020, covering every state. Using two different serology platforms, they tested the blood for SARS-CoV-2 antibodies, assuming only a positive result in both was significant. There were 9 samples that met this assumption and were from residents of Illinois, Massachusetts, Mississippi, Pennsylvania, and Wisconsin. The two earliest cases were samples collected Jan. 7 in Illinois and Jan. 8 in Massachusetts, and since antibodies most often appear two weeks after infection, both people must have become ill no later than Christmas.
The CDC also conducted its own study, using a similar methodology to analyze 7,000 blood samples donated in routine Red Cross campaigns between Dec. 13, 2019, and Jan. 17, 2020. In that case, as many as 106 samples tested positive for SARS-CoV-2 antibodies, with the first cases of illness occurring in California, Oregon and Washington, all around Dec. 13. And while the debate about the actual efficacy of the serological tests has continued unabated over the past year, the technology is improving literally month by month and scientists are confident in the reliability of their results.
Especially since both centers conducted additional testing of positive samples to be absolutely sure. This means that we still have no idea how long SARS-CoV-2 had been circulating among us before it was identified, but there are many indications that it was longer than we think. Only that most likely the cases were not many, and the unfavorable multiplication conditions caused these small outbreaks to die out on their own before they had time to cause the pandemic we saw later.