#18,629
Presumably only a small percentage of HPAI H5 infected mammalian wildlife are ever found and tested, but this week the USDA's list has reached a milestone of sorts, surpassing 500 entries. Four of the ten entries added this week are feline (3 house cats, 1 bobcat), while a new species - the Black Rat (n=4) - makes its first appearance.
House cats were only first added to the list in May of 2024, and since then 89 have been added. Other felines (bobcats, mountain lions, tigers, etc.) add more than 5 dozen more to the list.
Rodents, were first added in June of last year, and now (deer mouse, house mouse, black rat) make up > 20% of the the list (n=108).
- Last August, in Pathogens: Susceptibility of Synanthropic Rodents to H5N1 Subtype HPAI Viruses, we looked at a study where researchers challenged several rodent species (house mice, brown rat, black rat) with two (older 2010, 2007) HPAI H5N1 viruses, and found they are both susceptible to the virus and could potentially play a role it its evolution and spread.
- Also in August 2024, in Emer. Microbe & Inf.: HPAI Virus H5N1 clade 2.3.4.4b in Wild Rats in Egypt during 2023, we a surprisingly high percentage of wild rats testing positive for H5 antibodies in Egypt, suggesting that some number may survive the infection.
The USDA's list is far from exhaustive, since many states have reported zero - or only a few - infections. Reporting is often limited by animals dying in remote and difficult to access places, or by animals that survive the infection.
It is fair to say that what is reported is just the tip of the pyramid.
Not so very long ago, HPAI H5 was pretty much just an avian virus, with only occasional spillovers to humans and a few cats unlucky enough to be fed a diet of raw chicken. But starting in 2021 we began to see reports of numerous spillovers into a much wider range of mammals (see chart below).
Meaning that even if we somehow manage to control this virus in the henhouse and the dairy, it could still deliver a nasty surprise down the road.
