A few days ago, I wrote about a potential H1N1 influenza outbreak in dogs in California.  As I mentioned, H1N1 influenza causing an outbreak in dogs would be noteworthy because it’s not a known canine flu strain, and an outbreak would be unexpected given how rare it is to have human-to-dog transmission of human H1N1 influenza.

One of my key questions about the preliminary report was “Is this really on outbreak of H1N1, or is it a different flu strain?

It turns out it wasn’t H1N1 after all.

Follow-up testing apparently indicated that the outbreak was caused by H3N2 canine influenza virus. That’s still noteworthy, since we haven’t see much (diagnosed) flu activity in dogs for the last year or two in the US. We assumed the virus was still lingering in the dog population and causing smaller, more local issues that weren’t diagnosed or reported.  This outbreak and an outbreak of presumed canine influenza in Florida in June 2021 are consistent with that.

Overall this is good news. I’d rather be dealing with a sporadic, endemic, known entity (for which we have a vaccine) like H3N2 canine influenza, than a potentially new flu virus in dogs.