H5N1 updates put cats and dairy surveillance back in focus

Two seemingly separate H5N1 developments, a dead outdoor cat in Washington state and antibody-positive dairy cows in the Netherlands, point to the same larger issue: spillover into mammals is still happening, and cats may be among the clearest early signals for veterinary teams. Washington state’s H5N1 update, current as of February 17, 2026, lists one confirmed domestic cat case in Grant County, detected January 20, with wild birds as the suspected source. In the Netherlands, investigators first found H5N1 antibodies in one cow on a Friesland dairy farm after a farm cat tested positive, then later identified antibodies in five cows on that same farm. (cms.agr.wa.gov)

The Dutch case matters because it extends a pattern first recognized in U.S. dairy cattle in 2024, but with notable differences. A UK government preliminary outbreak assessment says the Netherlands report was the first detection of H5N1 antibodies in dairy cattle outside the U.S. and notes that no active infection was found in sampled cows. Wageningen University reported that the first antibody-positive cow had shown mastitis and reduced milk production in mid-December, then recovered, while all PCR tests on the farm were negative. That contrasts with U.S. dairy outbreaks, where virus was detected in milk and outbreaks spread across multiple states. (assets.publishing.service.gov.uk)

The cat angle is just as important. Scott Weese, writing in Worms & Germs Blog, highlighted that the Washington case fits a familiar pattern: cats are most often infected after outdoor exposure or ingestion of contaminated raw poultry products, and outcomes are often severe or fatal. Washington’s 2025 guidance for companion animal veterinarians similarly notes increasing feline detections tied to infected dairy farms and contaminated raw animal products, including raw milk and raw pet food. That guidance also says there is no evidence of cat-to-cat or cat-to-human transmission, though investigations continue. (wormsandgermsblog.com)

Broader feline surveillance data help explain why these reports are getting so much attention. A 2025 systematic review in Open Forum Infectious Diseases identified 607 avian influenza infections in felines reported from 2004 to 2024, with domestic cats making up 62.6% of cases. The review found a sharp rise in reports in 2023 and 2024, and estimated a 71.3% case fatality rate among RT-PCR-confirmed feline infections. International Cat Care’s response to that review has emphasized practical prevention steps for pet parents, including avoiding raw poultry and unpasteurized milk, a message that aligns closely with state veterinary guidance in Washington. (pmc.ncbi.nlm.nih.gov)

Industry and public health reaction has been notably measured so far. The European Centre for Disease Prevention and Control said on January 27, 2026, that its human risk assessment was unchanged after the Dutch dairy finding: low for the general population, and low to moderate for people with occupational or other direct exposure to infected animals or contaminated environments. Wageningen also stressed that no virus particles were found in the Dutch cow, meaning the animal was not shedding virus at the time of testing, and that milk entering the food chain was restricted to pasteurized products while the investigation continued. (ecdc.europa.eu)

Why it matters: For veterinarians, the practical takeaway is less about alarm than case recognition and exposure history. Cats with acute neurologic or respiratory signs, especially those with outdoor access, farm exposure, or diets containing raw poultry, raw milk, or raw pet food, now warrant a more deliberate H5N1 differential. On farms, unexplained cat deaths may be a useful trigger for broader herd or flock assessment. The Dutch investigation also raises a harder surveillance question: if cattle can experience mild or clinically silent infection, passive detection alone may miss early spillover events. (wormsandgermsblog.com)

That surveillance challenge is exactly what Weese underscored in his commentary on the Dutch farm. He argued that multiple antibody-positive cows make a false positive less likely and, while not proving it, increase concern about possible cow-to-cow spread. Wageningen’s public Q&A was more cautious, saying wild birds remain the likely source and that a direct link between the infected cat and cow could not be confirmed or ruled out. Taken together, the expert view is that this is a meaningful signal, but not yet evidence of sustained cattle transmission in Europe. (wormsandgermsblog.com)

What to watch: The next key markers are whether additional Dutch or other European farms show serologic or PCR evidence of infection, whether any viral sequence data become available, and whether veterinary agencies expand guidance for feline testing, farm biosecurity, and exposure counseling for pet parents. For now, the pattern remains consistent: cats can be severely affected, cattle infections may be subtle, and both can provide an early readout of where H5N1 is moving next. (assets.publishing.service.gov.uk)