07 May 2026
CDC researchers identified serologic evidence of H5N1 infection in an asymptomatic veterinary professional following exposure to an infected domestic cat. This discovery marks the first documented instance of possible zoonotic transmission of the virus from a feline to a human.
Since 2021, the highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b has decimated wild bird and poultry populations across the United States. Recently, the virus has increasingly spilled over into mammals, including dairy cattle and domestic cats. In felines, the disease is often severe, frequently linked to the consumption of unpasteurized raw milk or raw meat. While human cases have occurred, they were previously tied to direct bird or cattle exposure; cat-to-human transmission remained undocumented until now.
Between November 2024 and January 2025, 19 domestic cats in Los Angeles County fell ill with severe respiratory or neurological symptoms after consuming raw animal products. Public health officials identified 139 individuals, including pet owners and veterinary staff, who were exposed to these cats. Although 30 exposed persons reported flu-like symptoms, all acute respiratory (RT-PCR) tests for H5N1 were negative. In April 2025, a subset of 25 participants underwent serologic testing to look for antibodies. One asymptomatic veterinary professional tested positive for neutralizing antibodies specific to the H5N1 clade 2.3.4.4b. This individual had performed multiple clinical duties, including animal restraint and intubation, without respiratory or eye protection. This case highlights a critical shift in the H5N1 landscape, proving that domestic cats can infect humans.
Vaughan A, Joyce A, Traub E, et al. Serologic Evidence of Highly Pathogenic Avian Influenza A(H5N1) Virus Infection in a Veterinary Professional Exposed to an Infected Domestic Cat - Los Angeles County, California, December 2024–January 2025. MMWR Morb Mortal Wkly Rep 2026;75:216–220.
See: Cats may spread H5N1 to humans and vice versa
