"Evidence is available"

Avian flu virus jumps from cow to cat

From Southeast Asia, a highly contagious variant of avian influenza spread worldwide from 2005, first in wild birds and farmed poultry, and later in mammals.

(Bild: APA/HELMUT FOHRINGER)

The H5N1 avian flu virus is most likely being transmitted from cows to cats and raccoons, according to researchers. "This is one of the first times we have seen evidence of efficient and sustained mammal-to-mammal transmission of highly pathogenic H5N1 avian influenza," researchers said.

The genome sequences of viruses recovered from dairy cows, birds, domestic cats and a raccoon from affected farms indicate transmission between species, writes a team of researchers led by Diego Diel of Cornell University.

Further mutations could also make the virus more dangerous for humans, the researchers fear.

The risk of human-to-human transmission remains low: "The sequencing of the entire genome of the virus did not reveal any mutations in the virus that would lead to improved transmissibility of H5N1 to humans," says Diel. However, the data clearly showed mammal-to-mammal transmission, "which is worrying as the virus can adapt in mammals".

Genotype B3.13 developed
Based on these and other findings, mainly through genetic studies, the researchers outline this sequence of events: Genotype B3.13 evolved in an unknown host animal. It was first detected in a goose in Wyoming, a peregrine falcon in California and a skunk in New Mexico at the beginning of 2024. Another unknown host animal, possibly a wild bird, then transmitted the virus to the cows, through which it then found further hosts - pigeons and other birds in addition to cats and a raccoon.

In the USA, the eleven cases of bird flu in humans since April 2022 have so far ended mildly and with mild symptoms. The people affected worked on poultry and cattle farms and probably contracted the virus directly from the animals.

Researchers are concerned that the virus could continue to adapt, potentially increasing its infectivity and transmissibility to other species, including humans.