Avian flu, or H5N1, is making headlines in the United States. The past few years have seen concerning signs of it spreading across the world – whether in chickens in Britain, sea lions in Peru, or Caspian seals in Russia. This time, it is has been confirmed in American cows, and the World Health Organization has warned that the risk of it spreading to humans is of “enormous concern”.
While it is early days, the hypothesis is that in late 2023, a single cow was infected by coming into contact with infected birds’ faeces, or having infected dead birds in its feed. This began cow-to-cow transmission, and potentially even cow-to-bird transmission. The US Centers for Disease Control and Prevention has also confirmed one human case of H5N1 in a farm worker, which could either represent cow-to-human (not seen before) or bird-to-human transmission.
