Subclade K, a new flu strain, detected in San Diego County

Subclade K, the flu variant that caused fall outbreaks in the United Kingdom and Canada, has been detected in San Diego County, the region’s public health department confirmed Wednesday.

Genetic analysis performed at the county’s new public health lab on four samples collected from local patients confirmed subclade K’s presence. Three of the samples collected in December showed the specific set of mutations associated with K, which is part of the H3N2 group of flu viruses. An analysis of a fourth sample collected in late September also showed K’s genetic fingerprint, suggesting that the rapidly spreading strain was present at some level, though the specific prevalence is not known.

With the U.S. Centers for Disease Control and Prevention’s most recent flu report, released on Dec. 20, showing that 90% of the H3 influenza viruses it analyzed were subclade K, it is no surprise that it has already gained a foothold in the region. Standard community-level characterization of circulating flu viruses does not routinely include the level of genetic analysis that goes beyond the hemagglutinin and neuraminidase proteins on virus surfaces, which leads to the commonly-referenced H and N numbers that many who follow the flu are familiar with.

But San Diego County’s new $96 million public health laboratory, which opened in June, has t...