There’s a bird flu epidemic in fur farms. (This is not great.)

Eurosurveillance reports on an ongoing epidemic that has seen a contagious strain of avian influenza, HPAI H5N1, jump from birds to mammals, where it’s spread from wild seagulls to Northern European fur farms:

To date, 27 July 2023, 20 affected farms in four municipalities of Central and South Ostrobothnia have been identified … with blue and silver foxes and their crossbreeds, raccoon dogs and minks being infected. The affected farms, which vary in size from 600–50,000 fur animals, house a total of 37,900 minks, 142,463 foxes and 5,400 raccoon dogs (a total of 185,763 fur animals, each farm rearing 1–3 species).

[A]ll the HPAI samples from fur animals are BB genotype. BB genotype is a H5N1 virus variant widely found in seagulls all over Europe, and similar to HPAI H5N1 present locally in gulls…, suggesting that at least the original exposure and transmission stems from exposure to the birds…. Transmission between fur animals is also supported by the general epidemiological pattern of several hundreds of sick and dead animals on the 20 farms (mortality on affected farms has been 2–4 times the normal rate and, at the peak of the outbreak, a large farm recorded almost 400 deaths in one day, which is 10 times the normal rate). The exact mechanism of the transmission within and between farms is, however, not yet known.

At present, it appears likely that transmission among fur animals is contributing to the evolution of the outbreak, and PB2 mutations associated with improved replication in mammalian cells have been detected in a subset of the fur animal cases. A well-recognised concern exists that prolonged replication of the HPAI H5N1 virus in a high-density mammalian population, such as the fur farms, might lead to viral forms that could more easily spread among humans…. As there is little prior experience of outbreaks similar to the one described here, it is not possible to predict the outcome.

I found out about this ongoing situation via Kai Kupferschmidt’s Mastodon.