The bird flu virus H5N1 has been detected for the first time outside the US in a cow in the Netherlands. Antibodies against the pathogen were found in the milk of the animal on a farm in the province of Friesland. The Friedrich-Loeffler-Institut in Greifswald confirms that no such case was previously known worldwide.
On a dairy farm in the Dutch province of Friesland, a cat died from an H5N1 infection on December 26. Subsequently, the cows on the farm were examined on January 15. Antibodies against the virus were found in milk samples from one cow, although the animal showed no symptoms at that time. However, in December, the cow had suffered from udder inflammation and breathing problems, which are typical signs of bird flu infection in dairy cows.
Further samples from other cows, taken on January 22, were negative. There is no indication of active virus spread among the animals, and the virus itself was no longer detected. The milk from the affected cow was not processed due to its health issues. Commercial milk products are safe, as pasteurization eliminates the virus.
It is unclear how the cat and cow became infected. The Friedrich-Loeffler-Institut (FLI) suspects contact with infected birds or contaminated materials such as feces, feed, water, or milking equipment. FLI Vice President Martin Beer described a massive but hardly noticeable infection wave among wild birds in Europe, with up to 25 percent of wild ducks in the Netherlands affected.
The risk to cattle in Germany remains very low according to the FLI, as long as it stays at this single case. Worldwide, H5N1 infections in cows have only been known from the US so far, where the outbreak since March 2024 has affected dozens of farms, pets, and people. The World Organisation for Animal Health (WOAH) reports 1,022 cases in mammals for 2024, compared to 459 the previous year. This increases the likelihood of the virus adapting to mammals.
