Ultimately, all coronavirus deaths are connected to Wuhan, but that’s not what UCSF microbiologist Dr. Charles Chiu means. He’s talking about different strains of the virus which can be detected with gene sequencing. So, for instance, the original Wuhan strain of the virus can be differentiated from the strain that formed the first U.S. hotspot in Washington state by looking for specific mutations.

Dr. Chiu, who has been studying the outbreak in the Bay Area hasn’t been able to test samples from the three early victims of the disease which Santa Clara officials announced yesterday, so consider this informed speculation:

A top Bay Area microbiologist said Wednesday that the discovery of COVID-19 in a Santa Clara County woman who died three weeks before the nation’s first recorded fatality appears to be part of a cluster imported from China that he has been tracking… Charles Chiu, director of the UCSF-Abbott Viral Diagnostics and Discovery Center, said he hasn’t yet sequenced the genomes of the three victims, but he suspects they were infected by the same coronavirus strain he had discovered in several early patients in Santa Clara County, the county with the most COVID-19 cases in Northern California. That virus, he said, is identical to the coronavirus strain in Wuhan, China, where the pandemic started, except for a single mutation. That suggests the county was one of the first entry points for the virus and hadn’t yet spread widely around the community. It’s China origin also indicates that it wasn’t community spread… Chiu said his laboratory sequenced four or five strains from samples collected in Santa Clara County in early March and found two strains that caused small clusters, but now appear to have been successfully isolated and controlled.

So sometime in very early February or late January, someone brought the virus directly from Wuhan and a few people were infected in Santa Clara County, but those early infections didn’t spread widely enough to create a significant cluster. However, the same story notes the tightness of the proposed timeline makes some investigators question this explanation.

Warner Greene, a senior investigator at the Gladstone Institutes, said the first cases were reported in China in late December, and they were mostly connected to a fish market in Wuhan. For someone with no travel history to have been infected in Santa Clara County in early or mid-January, just a few weeks after the first reported cases in China, seems unlikely, he said… “Certainly it’s possible someone traveled from Wuhan, but they would have had to have been at the market and then gone to San Francisco and then infected someone else. That timeline is getting very, very tight,” Greene said. “I’m really starting to question how long this virus has been circulating in humans.”

Hopefully we’ll get a follow-up on this once Dr. Chiu has had a chance to examine the virus found in those early cases, the first of which on Feb. 6 is the earliest death in the U.S. Until then this is one more issue over which even credentialed experts continue to disagree.