occurred in the U.S. before the world ever became aware of a dangerous new virus erupting in China.
“The studies are pretty consistent,” said Natalie Thornburg of the Centers for Disease Control and Prevention.
“There was probably very rare and sporadic cases here earlier than we were aware of. But it was not widespread and didn’t become widespread until late February,” said Thornburg, principal investigator of the CDC’s respiratory virus immunology team.
Such results underscore the need for countries to work together and identify newly emerging viruses as quickly and collaboratively as possible, she added.
The pandemic coronavirus emerged in Wuhan, China in late 2019. Officially, the first U.S. infection to be identified was a traveler — a Washington state man who returned from Wuhan on Jan. 15 and sought help at a clinic on Jan. 19.
CDC officials initially said the spark that started the U.S. outbreak arrived during a three-week window from mid-January to early February. But research since then — including some done by the CDC — has suggested a small number of infections occurred earlier.
A CDC-led study published in December 2020 that analyzed 7,000 samples from American Red Cross blood donations suggested the virus infected some Americans as early as the middle of December 2019.