Highly Pathogenic Avian Influenza A(H5N1) Virus Infection of Indoor Domestic Cats Within Dairy Industry Worker Households — Michigan, May 2024

Highly pathogenic avian influenza (HPAI) A(H5N1) virus, clade 2.3.4.4b, genotype B3.13 infection has been documented in cats on U.S. dairy cattle farms. In May 2024, the detection of HPAI A(H5N1) virus infection in two cats that were reported to be exclusively indoor, and that had respiratory and neurologic illness in different households, prompted an investigation by the Michigan Department of Health and Human Services and Mid-Michigan District Health Department (MDHHS/MMDHD). The cats' owners and household members were interviewed and offered testing for influenza A(H5) virus. The owner of one cat worked on a dairy farm but declined A(H5) testing; three other household members received negative A(H5) test results. The owner of the other cat lived alone and worked on multiple dairy farms transporting unpasteurized milk; this worker also reported getting splashed in the face and eyes by unpasteurized milk but declined A(H5) testing. Both workers were employed in a county known by MDHHS/MMDHD to have HPAI A(H5N1) virus, clade 2.3.4.4b, genotype B3.13-positive dairy cattle. In states with confirmed HPAI A(H5N1) in livestock, veterinary care can be aided if veterinarians obtain household members' occupational information, especially when evaluating cats with signs of respiratory or neurologic illness. If occupational exposure to HPAI A(H5N1)-infected livestock is identified among cat owners, and their companion cats are suspected to have HPAI A(H5N1) virus infection, it is important that veterinarians contact state and federal public health and animal health officials to collaborate on joint One Health investigations and testing to protect human and animal health.