So is he saying the virus has already mutated? Or just that some of those who flew out from China before the travel ban had already infected some people in the at large community?
He is saying this unknown infected person had the same virus as the first infected person in the US. That means community transmission possible for 6 weeks.
He says it means that this case was directly infected by the Snohomish case 6 weeks ago, and also means it has been silently spreading for 6 weeks. He estimates a few hundred cases.