Yesterday, I discussed a situation where avian flu was suspected in the deaths of a reasonably large number of cats in Poland. “We need more information” was a big part of that, and as of today a few new pieces of the puzzle have come to light.

It’s now reported that H5N1 was detected in 9 of 11 samples from cats. Positive samples were from three different cities, which is a very important finding. A reasonably large number of cats affected (and this likely being the tip of the iceberg) from multiple different cities definitely raises concern, since this wasn’t just one group of cats exposed to the same infected bird or group of birds. Bird-to-cat jumps must have happened multiple times in multiple locations, and that’s not good.

Why might there be a large number of affected cats in this case?

The most logical explanation to me is that there’s a big outbreak of avian flu in the types of birds with which cats have more contact. Birds that live in cities and are more likely to be caught and eaten by cats. In parallel, there could be greater awareness of the risk of transmission of H5N1 to cats, so people are looking for and testing sick cats.

Regardless, this shows us we need to keep investigating. “Dozens” of potentially affected cats is still a pretty small number in the grand scheme of things, but it’s a lot for an infection that has been assumed to be a rare event, particularly considering we likely detect only a small minority of spillover events into animals. Every spillover to a mammal creates more opportunity for the virus to adapt to mammals (including humans), and when the virus infects domestic animals or animals with which people or domestic animals have more contact, spillovers increase the risk of human exposure. We’ve been fortunate that the serious impacts on mammals have, so far, avoided people. However, it’s a dynamic situation and we need to be vigilant (but not paranoid).

  • We need continued research to figure out what’s happening.
  • We need to use basic preventive measures to reduce spillover into domestic animals.
  • We need to prioritize vaccine development for humans and domestic animals in case it’s  needed.