H5N1 updates put cats back at the center of surveillance

CURRENT FULL VERSION: H5N1 surveillance is again converging on cats. A recent Washington state cat death and new follow-up findings from a Dutch dairy farm both point to the same lesson: feline infections may be one of the clearest early warnings that avian influenza has crossed into new settings. In Washington, an outdoor cat tested positive after likely exposure to wild birds. In the Netherlands, a farm investigation that began with a cat case has now identified H5N1 antibodies in five cows on the same dairy operation. (wormsandgermsblog.com)

The Dutch case has been building for months. In late December 2025, Dutch authorities were notified about two sick cats, one of which tested positive for avian influenza and died two days later. That triggered source and contact tracing, which linked the cat to a dairy farm in Noardeast-Fryslân, Friesland. Initial screening found one cow with H5N1 antibodies, and Scott Weese later reported that the total had risen to five cows with antibodies on the farm. (nvwa.nl)

What makes the Dutch finding notable is what investigators did, and didn’t, find. Wageningen University & Research said no virus particles were detected in the seropositive cow, and PCR testing of sampled animals was negative, indicating no active shedding at the time of testing. The cow had reportedly shown mastitis and reduced milk yield in mid-December, then recovered. Dutch authorities also said there were no signals of spread to other dairy farms, and the farm’s milk was restricted to pasteurized products while the investigation was underway. In other words, this looks more like evidence of prior infection than proof of the kind of active, milk-associated transmission seen in U.S. dairy cattle in 2024 and 2025. (nvwa.nl)

The Washington cat case adds a different but equally important signal. Weese noted that the reported exposure was thought to be wild birds, not contaminated food, a reminder that raw diets are not the only route veterinarians need to consider. Cats with outdoor access, barn cats, and cats on farms remain at risk from hunting, scavenging, or environmental exposure. That fits with broader U.S. experience: Cornell’s Animal Health Diagnostic Center advises testing cats with neurologic disease, respiratory illness, or histories that include raw milk, raw meat, contact with sick or dead birds, or farm exposure. (wormsandgermsblog.com)

The wider feline literature helps explain why these cases matter. A 2025 systematic review of two decades of published avian influenza infections in felids identified about 607 reported infections, including 302 deaths, with domestic cats accounting for 62.6% of cases. Among RT-PCR-confirmed feline infections, the overall case fatality rate was 71.3%, and nearly all deaths were linked to highly pathogenic strains, predominantly H5N1. The review also found a sharp increase in reports in 2023 and 2024, tracking with the spread of clade 2.3.4.4b in birds and mammals. International Cat Care, responding to the review, emphasized that infections in cats have been reported globally, most often in Asia but also in Europe and North America, and highlighted that some infected cats may show no clinical signs at all. The most commonly reported signs were respiratory disease, neurologic abnormalities, and blindness. (pmc.ncbi.nlm.nih.gov)

There’s also growing debate about how broadly veterinary teams should think about transmission risk. A STAT commentary by veterinarians and biosecurity experts argued that rising H5N1 activity in cats warrants stronger surveillance and noted that more than 100 domesticated cats in the U.S. had confirmed infections since 2022. The authors pointed to a CDC report on two indoor cats in Michigan dairy worker households as evidence that infected people, contaminated clothing, or other indirect household exposures may also be plausible routes, though some outside experts have cautioned that the evidence does not conclusively prove human-to-cat transmission. International Cat Care’s summary of the feline review likewise noted that most reported cases appear to be bird-to-cat transmission, especially through predation, scavenging dead birds, contaminated raw poultry, or raw milk from infected cattle, but it also pointed to past reports in which feline-to-human transmission was linked to infected tigers in Thailand and to a cat shelter outbreak in New York. (statnews.com)

Why it matters: For veterinary professionals, these updates reinforce that cats are not just spillover victims, but potentially useful surveillance sentinels at the animal-human-environment interface. A dead or neurologic cat may be the event that reveals H5N1 exposure on a farm. That has implications for small animal practice, farm calls, shelter medicine, diagnostics, PPE use, and client counseling for pet parents, especially around outdoor access, wild bird exposure, raw meat diets, and unpasteurized milk. The prevention advice is also becoming more concrete: avoid feeding raw poultry or unpasteurized milk, keep farm cats from drinking on-farm milk, promptly evaluate cats with respiratory or neurologic signs, and counsel owners on reducing hunting and scavenging opportunities where feasible. It also argues for close coordination between companion animal veterinarians, livestock practitioners, diagnostic labs, and public health teams when feline cases surface. (nvwa.nl)

What to watch: The key next questions are whether Dutch investigators document any additional seropositive cattle or viral detections, whether more feline cases uncover hidden farm or wildlife exposure chains, and whether veterinary guidance in the U.S. and Europe shifts toward more routine H5N1 consideration in cats with acute neurologic or severe respiratory disease. Also worth watching is whether public-facing guidance expands beyond foodborne risk to include practical measures to limit bird predation and scavenging in at-risk cats. (nvwa.nl)