Researchers from the Centers for Disease Control and Prevention (CDC) conducted a study of 7,000 blood bags. They were collected by the American Red Cross between December 13, 2019 and mid-January 2020. This happened long before the official declaration of the first case of Covid-19 in the United States, which dates back to January 20, 2020. Now, 106 samples among 7,000 have been labeled positive for Covid-19 associated antibodies.
Note that the samples come from nine US states. More than half of the patients who test positive for the disease come from Massachusetts, Michigan, Connecticut, Rhode Island, Iowa and Wisconsin. The remaining 39 come from Washington, California and Oregon.
The results of this new study question the date when the virus actually started spreading on American soil.
False positives or positive cases?
As a reminder, the Chinese state reported the first cases of this crippling pneumonia in late December 2019. It was in Wuhan, the capital of Hubei.
It should be noted that a positive test for coronavirus antibodies only suggests infection with the SARS Cov-2. The possibility of false positives between samples should not be excluded. They are mainly due to the host reaction against other types of coronaviruses.
Then, to refine their results, the CDC researchers ran further tests. They analyzed the collected samples for reactions to SARS Cov-2 antibodies. Finally, 84 out of 90 analyzes are positive. “The results make it very unlikely that all samples are false positives”, they concluded. In other words, the team is almost certain that a good number of these patients have been infected with Covid-19.
Read also: Covid-19 vaccine, the 5 steps recommended by the HAS
Still some gaps to be filled
University of California epidemiologist Dr. George Rutherford, who is also a professor of biostatics in San Francisco, pointed to the study’s limitations. For him, in addition to the possibility of a cross-reaction with other types of coronavirus, the research has another flaw. These are the data on the exact places where people who tested positive contracted the virus. For example, the study questionnaire does not consider possible trips abroad.
Read also: We know who the first doses of the Covid-19 vaccine will go to in the United States
Dr Rutherford said more studies are needed to verify these findings. He specifically recommended the search for SARS Cov-2 genetic material on these positive samples. This should be based on an analysis of the saliva, blood and tissue of the first Americans who test positive.