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Five weeks ago - for the very first time - the USDA began adding infected domestic cats to their Mammals with H5N1 list. While we'd seen sporadic reports of H5N1 in American cats previously (see here & here) - and in other countries (see Poland, South Korea, and France) - since the spillover into cattle reports had suddenly accelerated.
That first report included 16 cats, going back to March. All but one (from Montana) came from states already reporting H5N1 in dairy cows.
Since then, we've seen that number steadily rise, and while likely an undercount, the total (since March) now stands at 30, with Texas, Michigan, and New Mexico topping the list, each reporting 7.
Mammals - including domestic cats - often die in remote and difficult to access places where their carcasses are quickly scavenged by other animals, meaning most never discovered or tested. And of course, some of these animals are likely to survive the infection, and are never tested.
Of those, 7 states (Arizona, Florida, Illinois, Missouri, Ohio, Rhode Island, and Vermont) have only reported a single incident, while New Mexico leads with 78 (including 66 mice from a poultry farm).
It is probably fair to assume that some states are looking harder than others, but other factors - including differences in terrain and climate - may be hindering investigations.
With so much H5 circulating in the wild, one of the concerns is the potential for companion animals (primarily cats) to bring avian influenza from the wild into the home (see A Brief History Of Avian Influenza In Cats). While the risk is considered low, it is not zero.Although dogs are also susceptible to H5N1 (see EID Journal: Antibodies to Influenza A(H5N1) Virus in Hunting Dogs Retrieving Wild Fowl, Washington, USA ), they tend to have milder (often asymptomatic) infections.
While the CDC considers the risks to humans from H5N1 to be low, they offer a web page with extensive advice for pet owners.
