Vet Times A study examined the B3.13 genotype of H5N1, which has been circulating in US dairy herds since 2024. One study, published in Nature Communications, examined the B3.13 genotype of H5N1, which has been circulating in US dairy herds since 2024.
Researchers discovered several mammalian adaptations in cattle, enhancing replication in bovine and human cells.
Virus sequences
One such mutation (PB2 M631L) was found in all cattle virus sequences studied, while another – PA K497R – appeared in around 95%. The former was described as “the key adaptive mutation” that allowed the B3.13 genotype to efficiently replicate in cattle.
Further mutations, PB2 E627K and PB2 D740N, were said to indicate ongoing adaptation of H5N1 viruses to further optimise polymerase function in cattle. Both appeared to have little or no negative impact on replication in birds, suggesting the mutations could be maintained if the viruses spill back into avian species.
The study concluded that, “in the absence of an effective control strategy, the high pathogenicity H5N1 virus may now become endemic in US dairy cattle” and that urgent vaccine development and testing is a “priority”.