The novel coronavirus was circulating undetected in the United States for weeks in December—about a full month before the first confirmed case in the country, according to a new study that has been published in the journal Clinical Infectious Diseases.
The eye-opening research arrived at its conclusion after the U.S. Centers for Disease Control and Prevention found evidence of coronavirus antibodies in blood collected in December 2019. The samples had been gathered originally to test for exposure to mosquito-borne illnesses like the West Nile virus.
After analyzing blood donations collected by the American Red Cross from individuals in nine states between December 13 and January 17, the researchers were eventually able to see that antibodies were present in 106 out of 7,389 samples.
The first coronavirus-positive patient was diagnosed on January 20 in Washington state, according to the CDC.
“These findings suggest that SARS-CoV-2 may have been introduced into the United States prior to January 19, 2020,” the researchers wrote.
Medical experts are open to the idea that the coronavirus could have been spreading in the United States before the first official case, but it is also possible that serological testing may have pinpointed a different strain or type of coronavirus. Antibodies for SARS-CoV-2 are known to look similar to other coronaviruses that can cause illnesses like the common cold.
Other studies have also suggested an earlier start to the pandemic. Just last month, new research out of Italy made headlines when the authors suggested that the coronavirus was likely already present in the city of Milan last September—a full five months before the country’s first coronavirus-positive patient was detected and three months before the initial outbreak was reported in Wuhan, China.
After the study’s publication, some scientists argued that the findings had the potential to change the origin history of the ongoing pandemic and called for further tests. The authors responded by saying that the study’s results do not in any way dispute the Wuhan origin of COVID-19.
In another research conducted in May, a genetic study out of England suggested that the novel coronavirus was circulating around the world as early as October. The scientists were able to identify nearly two hundred recurrent genetic mutations of SARS-CoV-2, which researchers said showed how the virus was adapting to its human hosts as it spreads.
“Phylogenetic estimates support that the COVID-2 pandemic started sometime around October 6, 2019 to December 11, 2019, which corresponds to the time of the host jump into humans,” the research team wrote in the journal Infection, Genetics and Evolution.
The World Health Organization had previously stated that the novel coronavirus was not circulating elsewhere before Wuhan began implementing measures to contain the contagion.
Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.