Review details H5N1 avian flu risks and symptoms in domestic cats

For decades, the domestic cat was treated as an accidental host of influenza A viruses. The worldwide spread of highly pathogenic H5N1 virus of clade 2.3.4.4b brought felines to the centre of attention. A review published on 24 August 2026 in Veterinaria Italiana, the journal of the Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise, gathers what is known about the epidemiology, pathogenesis, clinical presentation, diagnosis and One Health implications of H5N1 infection in cats.

According to the review, beyond the traditional route of predation on infected wild birds, recent outbreaks revealed new exposure routes: contaminated commercial raw poultry products and unpasteurised milk. Cats' susceptibility is attributed to the abundant distribution of α-2,3-linked sialic acid receptors in both the respiratory tract and the central nervous system, and adaptive mutations such as PB2-E627K may enhance replication efficiency in mammals. The clinical picture combines severe respiratory, neurological and ocular manifestations, including acute bilateral amaurosis, and is associated with high mortality rates.

The link to raw milk has a documented origin. In 2024, Emerging Infectious Diseases reported clade 2.3.4.4b infection in dairy cows in Kansas and Texas: the cows showed non-specific illness, reduced feed intake and rumination and an abrupt drop in milk production, while domestic cats fed raw colostrum and milk from affected cows developed fatal systemic infection. Cow-to-cow transmission became evident when animals moved to farms in Michigan, Idaho and Ohio carried the infection with them.

A study published in Nature the same year detailed the mechanism. Infectious virus and viral RNA were consistently detected in milk from affected cows, and the virus's distribution in tissues revealed a tropism for the epithelial cells lining the alveoli of the mammary gland. Whole genome sequences recovered from cows, birds, domestic cats and a raccoon on affected farms indicated multidirectional interspecies transmission. The 2026 review also records recent documentation of feline-associated zoonotic transmission, which, for the authors, reinforces the importance of surveillance and infection control in veterinary settings.

The World Organisation for Animal Health (WOAH) states on its avian influenza page that the virus can cross the species barrier to infect domestic and wild terrestrial and marine mammals, with cases recorded on mink farms and in wild foxes and cats. The organisation describes cats as unusual hosts and considers the risk of transmission from a sick cat to a person currently very low or negligible; even so, it recommends protective equipment when handling suspected cases, avoiding contact with sick birds and contaminated surfaces, and encourages countries to monitor and report, through the WAHIS system, occurrences in animals other than birds.

For the small animal veterinarian, the review sums up the task in three moves: recognise a compatible syndrome early, especially respiratory and neurological disease with a history of exposure to birds, raw products or raw milk; seek rapid molecular diagnosis; and apply biosafety measures during care. This summary describes the state of published knowledge and does not replace official surveillance protocols or the clinical assessment of each case; when a case is suspected, the guidance of the country's official veterinary service should be followed.