Following the discovery of the dangerous avian influenza virus A (H5N1) in dairy cows in the USA, the World Health Organization (WHO) has reiterated existing recommendations to consume pasteurized rather than raw dairy products.

In Texas, a man who worked on a cattle farm tested positive for the virus. Exactly how the transmission occurred is still being investigated, said Wenqing Zhang, head of the WHO influenza program, in Geneva. It is the first known case of transmission from a cow to a human.

“Human infections with A(H5N1) remain rare and are related to contact with infected animals and the environment,” she emphasized.

The US authorities informed the WHO about the man’s infection at the beginning of April and also reported that the virus had been found in unpasteurized milk. According to US information, the man only had mild symptoms, such as red eyes that resembled conjunctivitis. According to US information, cows are probably infected by wild birds.

So far, the virus has only been found in dairy cows in the USA

According to the WHO, 29 herds in eight states are affected. Analyzes of the virus have shown that it has no changes that make it more adaptable to mammals, Wenqing said.

“Transmissions from birds to cows, from cows to cows and from cows to birds have also been recorded in the current outbreaks, suggesting that the virus may have found other transmission routes than we previously thought,” Wenqing said.

The highly pathogenic avian influenza virus A(H5N1)  first emerged in 1996, but since 2020, infections among birds have been increasing rapidly, affecting more and more mammals, including minks, seals, sea lions and foxes. The largest wave of bird flu ever documented is currently raging across almost the entire world and also affecting Europe. The WHO is currently working with partners on a new risk assessment related to (A)H5N1.

According to WHO, almost 900 cases of A(H5N1) infections in humans have been reported since 2003. Half of them died. However, according to the WHO, it cannot be ruled out that many more people were infected but did not show any symptoms and the cases were therefore not discovered.