Highly pathogenicity avian influenza viruses (HPAIV) H5Nx of clade 2.3.4.4b have circulated extensively in recent years and become enzootic in many regions since 2020. This increased circulation has led to greater exposure of mammals to these viruses. Cats are known to be susceptible to infection by HPAIV H5Nx, with cases — sometimes serious or fatal — reported following contact with infected birds and the ingestion of contaminated raw meat or milk. A Dutch study recently identified a 11.8% and 0.46% seropositivity rate among stray and domestic cats respectively, highlighting their potential role as sentinels for carnivorous mammals’ exposure to HPAIV H5Nx.

Our study aimed to provide an estimation of the seroprevalence against two HPAIV H5Nx types in France.