Research has revealed a link between dairy farms and the H5N1 virus in domestic cats.

During a study conducted in California's Central Valley from December 2024 to March 2026, experts examined blood samples from 73 domestic cats. The livestock animals resided within a radius of up to 9.7 km from dairy farms. Laboratory tests using ELISA and microneutralization confirmed the presence of antibodies to the influenza A(H5N1) virus, clade 2.3.4.4b, in three individuals.

The results showed that among cats living within a 2 km radius of livestock facilities, the seropositivity rate was 25%. The average distance from the living areas of seropositive cats to the nearest dairy farm was 1.34 km, whereas for seronegative ones this figure was 4.83 km. All identified infection cases were recorded in animals in rural areas.

The study authors note that in cats, the H5N1 virus is associated with a high mortality rate, estimated at 90%. The observed seroprevalence may be underestimated, as serious complications, including encephalitis, paralysis, and blindness, often lead to the death of the animals before examinations can be conducted. Possible transmission routes for the virus include direct contact with infected livestock, consumption of infected raw milk, or infection transmission via poultry.

Two of the three seropositive cats were kept exclusively indoors and belonged to dairy industry workers, which allows for the possibility of virus transmission from humans. At the same time, in the study group, cases of feeding on raw meat or milk were not confirmed. The researchers emphasize the importance of prevention and suggest that vaccination of the dairy herd could reduce risks for animals located near farming operations.

This work supplements information on the spread of the H5N1 virus, cases of which were previously recorded among cats in Texas, New Mexico, Minnesota, South Dakota, and Michigan. The obtained data indicate a need for further study of virus transmission routes and measures to protect domestic animals in high-risk zones.