H5N1 reports in a Washington cat and Dutch cow raise new flags

Two new H5N1 developments, one in a Washington state cat and one in a Dutch dairy cow, are reinforcing an uncomfortable reality for veterinarians: avian influenza surveillance can no longer stay confined to birds. In Washington, state agriculture officials confirmed that an outdoor cat in Grant County tested positive for highly pathogenic avian influenza after reported contact with a dead wild bird and later died. In the Netherlands, researchers detected H5N1 antibodies in milk from a dairy cow on a Friesland farm, marking the first reported evidence of avian influenza exposure in cattle in Europe. (agr.wa.gov)

Neither event was entirely unexpected. Cats have repeatedly been infected through exposure to infected birds, contaminated raw foods, and, in the U.S. dairy outbreak, raw milk from infected cows. Meanwhile, since the U.S. dairy cattle outbreak emerged in March 2024, European researchers and regulators have been watching closely for signs that similar spillover could occur in local cattle populations. Wageningen researchers had already reported no indication of widespread H5N1 infection in archived Dutch cattle samples, but they also noted that surveillance gaps and uncertainty about antibody persistence left room for missed past exposure. (wwwnc.cdc.gov)

The Washington case appears to fit the classic feline spillover pattern. The state’s January 27, 2026 announcement said the cat was an outdoor pet, had contact with a deceased wild bird, tested positive for H5N1, and died. State materials for veterinarians emphasize that domestic cats in the general population are still considered low risk overall, but they can develop severe disease, often progressing to pneumonia and sometimes neurologic signs, after exposure to infected birds or contaminated animal products. Washington has also been advising veterinarians and animal facilities to use heightened PPE when H5N1 is suspected in cows, birds, or other animals. (agr.wa.gov)

The Dutch finding is more nuanced, but potentially just as important. Wageningen University & Research said the seropositive cow was investigated after avian influenza had already been confirmed in a cat on the same dairy farm. Milk samples from 20 cows and a bulk tank sample were collected as part of monitoring, and antibodies were found in one cow, indicating past infection or exposure. No virus particles were detected in that animal, and the European Centre for Disease Prevention and Control said the finding did not change its public health risk assessment. A later UK risk document added that Dutch follow-up work identified four other cows with antibodies, though viral RNA was not detected from blood samples, underscoring how serology may reveal exposure that routine virologic testing misses. (wur.nl)

Outside these two incidents, the broader literature is pushing the veterinary conversation toward cats more urgently. A 2025 systematic review in Open Forum Infectious Diseases identified 607 avian influenza infections in felines from 18 countries over two decades, including 302 associated deaths, and found that domestic cats accounted for more than 60% of reported cases. The authors warned that free-roaming cats, farm cats, veterinarians, shelter workers, and others in close contact with exposed animals may face elevated risk during outbreaks. International Cat Care’s response to that review similarly urged pet parents to avoid feeding raw poultry or unpasteurized milk and to reduce cats’ contact with wild birds. (academic.oup.com)

Why it matters: For veterinary professionals, these reports sharpen both clinical suspicion and biosecurity planning. In small animal practice, H5N1 belongs on the rule-out list for cats with sudden respiratory or neurologic illness plus outdoor exposure, hunting behavior, raw diet history, or access to raw milk. In mixed and large animal settings, the Dutch cow finding suggests that even in the absence of obvious herd-level illness, targeted surveillance around mammalian spillover events, especially infected farm cats, may be worthwhile. The U.S. experience showed that cattle infections can circulate more widely than first recognized, with one CDC-linked retail milk study arguing that undetected herd transmission likely occurred for months before the outbreak was identified. (cms.agr.wa.gov)

There’s also a communication challenge. Pet parents may still think of bird flu as a poultry issue, not a cat issue, and some may underestimate the risk from raw feeding or outdoor predation. For veterinarians, that makes preventive counseling more concrete: keep cats indoors when possible, avoid raw poultry and unpasteurized dairy, use PPE when evaluating suspect cases, and coordinate quickly with state animal health officials when H5N1 is on the table. Those are familiar recommendations, but the Washington and Dutch reports show why they’re increasingly relevant across companion animal and farm practice. (cdc.gov)

What to watch: The next key signals will be whether Dutch surveillance uncovers broader cattle exposure or active infection, whether more feline cases are formally tested instead of presumed, and whether regulators in Europe and the U.S. adjust surveillance protocols for cats and cattle as mammalian spillover continues to evolve. (assets.publishing.service.gov.uk)