A paper in December’s Emerging Infectious Diseases (Marinova-Petkova et al, Avian influenza A(H7N2) virus in human exposed to sick cats, New York, USA, 2016) follows up on the shelter outbreak and human infection that was reported widely at the time (and which was summarized earlier this year). This paper describes investigation of the virus from the infected person and from a cat at the shelter.
The take home is that they were almost identical, meaning it’s pretty certain that the person was infected by an animal at the shelter. The study also showed that the virus was very similar to a low pathogenicity avian flu strain that was circulating in the US in the early 2000s.
Presumably, this strain is still circulating in birds, and it happened to spill over into a cat. (Outdoor cats that hunt are at risk of exposure). Then, an infected cat (during the short period it was infectious) happened to enter the shelter, have contact with other cats (again, during that short period when it’s infectious), with transmission to more cats and ultimately a person working with them.
It’s an interesting scenario, for sure. However, it’s not overly concerning.
- We know flu strains can periodically infect cats.
- This outbreak burned itself out pretty quickly.
- There was just one known human infection, and it was from someone with close contact with the cats.
- The fact that a cat would get infected, go into a shelter and have contact with other cats in the shelter during what is likely a few day window of being infectious is pretty unlikely. Often, strange disease events are ‘perfect storm’ manifestations like this. The odds of any given cat carrying influenza virus at any time are exceptionally low.
This is a good reminder of the potential for interspecies transmission of influenza virus and the potential for pets to act as bridges between wildlife and human disease. However, it’s important to keep things in context and realize this is an oddball scenario, not a sign of a new serious problem