The person who started the first chain of sustained transmission of the new coronavirus in the U.S. likely came into the country with the virus in mid-February, which throws into question the theory that sustained transmission began with the country's first case of COVID-19 in January, a new study suggests, according to STAT News.
For the study, which has not been peer-reviewed, researchers used genetic sequence data to examine the evolution of the coronavirus from the first confirmed COVID-19 case in the country. The patient who was identified as being the first case returned to Washington state Jan. 15 from Wuhan, China. Using a simulation model, researchers compared the genetic sequences of 300 simulated cases to the genetic sequences retrieved from 300 patients in Washington. The genetic sequences from the simulated model and actual patients did not match as they should have, had the Jan. 15 case been the source of sustained transmission.
This led researchers to conclude that the virus outbreak in Washington state, the first in the country, did not start with the person who returned to the country Jan. 15.
"It started with some unidentified person who arrived in Washington state at some later point. And we don't know from where," Michael Worobey, PhD, department head of ecology and evolutionary biology at the University of Arizona in Tucson and leader of the new research, told STAT.
The researchers estimate that the coronavirus outbreak in Washington state likely began with a person who returned to the U.S. around Feb. 13.
This shows that there was "an extended period of missed opportunity" when intensive virus testing and contact tracing could have stopped the new coronavirus from becoming established in the country, researchers concluded.
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