Serologic Evidence of Highly Pathogenic Avian Influenza A(H5N1) Virus Infection in a Veterinary Professional Exposed to an Infected Cat — Los Angeles County, 2024–2025
- Presentation Day/Time: Tuesday, April 21, 2:35 PM
- Presenter: Aisling Vaughan, PhD, MSc, Los Angeles County Department of Public Health
The Issue
- During November 2024–January 2025, 19 cats in Los Angeles County became ill after consuming commercially purchased raw milk, raw meat, and raw pet food, and nine tested positive for avian influenza A (H5N1) virus. In total, 139 persons were exposed to ill cats; all were monitored for symptoms and none tested positive for H5N1 using RT-PCR testing.
What We Did
- In April of 2025, the Los Angeles County Department of Public Health and CDC invited all exposed persons to participate in testing to look for H5N1-specific antibodies in their blood. Twenty-five persons were tested.
What We Found
- One veterinary professional who was exposed to an H5N1-infected cat was found to have H5N1-specific antibodies in their blood. They did not report any symptoms after exposure, and a nasopharyngeal swab obtained seven days after exposure was negative for influenza A using RT-PCR testing. No exposure to backyard poultry or wild birds or consumption of raw meat or dairy products were reported.
What This Means
- This finding represents serologic evidence of possible transmission of H5N1 from a domestic cat to a veterinary professional and raises new concern about potential zoonotic transmission of the virus, reinforcing the importance of infection control practices in veterinary settings.
