#18,530
After several months with only sporadic additions to their list, today the USDA has added 30 new H5N1 cases to their infected mammalian wildlife list (see below).Quite notably, 29 of the 30 additions were felines, with the vast majority being captive or domestic animals
Given the toll we've seen in captive felines, it is likely that a great many feral felines are infected, but are never counted. Additionally, some domestic cats may die, but are never tested.
Less than a month ago, in Emerg. Microbes & Inf.: Marked Neurotropism and Potential Adaptation of H5N1 Clade 2.3.4.4.b Virus in Naturally Infected Domestic Cats, we looked at a report on the HPAI H5 infection of a house full of domestic cats (n=8), all of which died, many with severe neurological symptoms.
But only 2 were actually tested, and so 6 of those cats did not make the list.
Isolates from the two cats that were tested showed signs of viral adaptation to a mammalian host. The authors wrote:
Cat H5N1 genomes had unique mutations, including T143A in haemagglutinin, known to affect infectivity and immune evasion, and two novel mutations in PA protein (F314L, L342Q) that may affect polymerase activity and virulence, suggesting potential virus adaptation.
Dead cats showed systemic infection with lesions and viral antigens in multiple organs. Higher viral RNA and antigen in the brain indicated pronounced neurotropism.
While the H5 virus currently lacks the ability to transmit efficiently from human-to-human, every mammalian infection is another opportunity for the virus to crack that code.
Which is why we need to be actively looking for - and testing - mammalian victims of this virus.
Because what we don't know, can hurt us.
