Story at a glance
- A team of U.S. researchers looked at blood samples leading up to the onset of the COVID-19 pandemic in the continental U.S.
- 106 samples presented evidence of infection.
COVID-19 was spreading throughout the continental U.S. prior to the first official recorded infection, according to a new study.
Looking at blood samples collected by the American Red Cross between Dec. 13 and Jan. 17, some blood donors from nine states tested positive for COVID-19 antibodies, indicating that they had come into contact with the virus prior to Jan. 20, when officials confirmed the first COVID-19 case in the U.S.
The study, published by the Oxford University Press for the Infectious Diseases Society of America, was authored primarily by U.S. government employees.
Retrospectively testing 7,389 blood samples donated to the Red Cross between December and January — all prior to the first confirmed COVID-19 case — researchers found that 106 specimens showed signs of COVID-19 infection.
Within this 106, 84 showed even greater reactivity when screened using a pan Ig enzyme solution.
The donors were sampled from California, Connecticut, Iowa, Massachusetts, Michigan, Oregon, Rhode Island, Washington and Wisconsin. They were collected from Red Cross banks and tested in Atlanta at the U.S. Centers for Disease Control and Prevention (CDC).
“These findings indicate that SARS-CoV-2 reactive antibodies were detected in 106 specimens, a small percentage of blood donations from California, Oregon, and Washington as early as December 13–16, 2019,” the authors wrote. “The presence of these serum antibodies indicate that isolated SARS-CoV-2 infections may have occurred in the western portion of the United States earlier than previously recognized or that a small portion of the population may have pre-existing antibodies that bind SARS-CoV-2 S.”
The average age of the blood donors tested in the study was 52 years old, ranging from 16 to 95 years of age. The proportion of reactive blood samples was higher among male donors than female donors, but male donations were more prominent during this timeframe.
These results follow news coming from leaked Chinese documents that revealed scientists working with the Hubei Provincial CDC recorded more cases in February than officially published.
Serologic tests featured in the U.S. study highlight the efficiency of using blood samples as a means to trace the virus, especially as many infected individuals boast only modest symptoms or are asymptomatic.