CDC confirms cat-to-human H5N1 case

The U.S. Centers for Disease Control and Prevention said this month it had documented evidence that a domestic cat transmitted H5N1 avian influenza to a human in Los Angeles County, the first such reported case in the United States. The finding appeared in the CDC’s Morbidity and Mortality Weekly Report on May 7 and involved a veterinary professional who was exposed while treating infected cats between December 2024 and January 2025. The worker did not develop symptoms, but later blood testing found evidence of infection. The agency said the broader risk to the public remains low, while advising pet owners and veterinary staff to take added precautions. ### How did investigators connect a cat exposure to a human infection? Los Angeles County public health officials and the CDC traced the case during an investigation into a cluster of sick domestic cats that had consumed raw animal products. The CDC said 19 cats became ill between November 2024 and January 2025 after consuming commercially purchased raw milk, raw meat, or raw pet food, and nine tested positive for influenza A(H5N1). (cdc.gov) Among 139 people identified as exposed to those cats, 25 later volunteered for serologic testing, according to the CDC. One asymptomatic veterinary professional had serologic evidence of H5N1 infection after occupational exposure to an infected cat, the report said. The agency said no cat-to-human transmission of H5N1 from domestic cats had previously been documented. ### Why was this case found months later instead of during the original investigation? (cdc.gov) The CDC said all 139 exposed people were initially monitored for symptoms. Thirty reported influenza-like illness, but none received a positive influenza A(H5) RT-PCR test result at the time, according to the report. In April 2025, Los Angeles County and CDC investigators invited exposed people to join a serosurvey to determine whether infection had occurred, including in people without symptoms. (cdc.gov) That follow-up blood testing is what identified the veterinary professional, the report said. ### What role did raw animal products play in the investigation? The CDC said the infected cats had consumed commercially purchased raw milk, raw meat, or raw pet food before becoming ill. (cdc.gov) The agency’s public-health takeaway was direct: pet owners should not feed raw animal products to cats. The American Veterinary Medical Association, citing the CDC report, said the investigation involved pet cats that had consumed raw animal products and later infected a veterinary worker. (cdc.gov) The association said health officials still consider the overall public risk low. ### What does the CDC want veterinarians and pet owners to do now? The CDC said veterinary professionals should be aware of infection risks, use appropriate personal protective equipment, and follow infection-control practices to reduce the risk of zoonotic transmission. (cdc.gov) The agency also advised pet owners not to feed raw animal products to cats. Since 2021, the CDC said H5N1 clade 2.3.4.4b viruses have spread widely among wild birds and poultry in the United States, with sporadic spillover into mammals. (avma.org) The Los Angeles County case adds domestic cats to the list of mammal exposures that public-health officials are watching closely. ### What happens next in this investigation? The CDC’s May 7 report remains the primary public record of the case, and trade and veterinary outlets including WATT Poultry and the AVMA highlighted the findings again in mid-May. (cdc.gov) Public-health guidance now centers on monitoring animal exposures, avoiding raw animal products for pets, and using protective gear in veterinary settings where H5N1 could be present. (wattagnet.com)