Epidemiologists believe that the first confirmed case of COVID-19 in the United States involving a Snohomish County traveler who fell ill in mid-Januarymay not have been the one who triggered the west coast coronavirus outbreak.
- The revised scenario is based on an analysis of hundreds of virus genomes and is described in a Research report that has not yet been reviewed by experts. The University of Arizona evolutionary biologist Michael Worobey and his colleagues focused on the January WA1 case, known as WA1, and a viral variant that spread to Washington State in late February and was known as WA2.
- Earlier analysis revealed that WA2 was a version of WA1 that mutated during spread, leading to the conclusion that WA1 must have infected hundreds of people in the meantime. The later analysis considers this scenario to be unlikely: Instead, WA2 seems to have come to the USA via China or maybe Canada later.
- The researchers said their analysis indicated that there was "a longer period of missed opportunities" in which intensive testing and contact tracking could have prevented the outbreak from spreading. Trevor Bedford, an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, who was involved in the earlier analysis, said in a Twitter thread that he now believes he is "wrong in the initial assessment of a WA1 launch, but right in claiming a significant spread of the community in Washington State on February 29".
Further information on the research report published on BioRxiv can be found at "The Formation of SARS-CoV-2 in Europe and the USA" Check out Carl Zimmer's report in the New York Times.
