Monday, March 8

Coronavirus may have been circulating undetected in the US for 6 weeks

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Coronavirus is quietly spreading in the US

Anthony Behar/Sipa USA

Covid-19 could already be circulating in the US, according to similar genetic sequences in viruses from two people who contracted the disease several weeks apart. One comes from a recent case in Snohomish County, Washington, in which the infected person had no contact with another case or outbreak location. Despite this, the sequence of the virus in their sample closely matches that in the first infection detected in the US, on 21 January, in a man in the same county who had visited Wuhan.

Both sequences, which were posted to …

We clarified who had been tested in the US.