Influenza A(H5N1) Virus in Sheep

The UK Department for Environment, Food & Rural Affairs (DEFRA) announced on 24 March 2025 the country's first detection of Influenza A(H5N1) Virus in Sheep in a sheep following repeat positive milk testing. This first case was detected on a farm in Yorkshire.

This case was identified following routine surveillance of co-located livestock on a premises where avian influenza had been confirmed in captive birds. In a separate announcement, DEFRA said the ewe's only clinical sign was mastitis, the animal's milk was positive for H5N1 on polymerase chain reaction testing, and a blood sample was positive for H5 antibodies.

The captive birds and the ewe were culled to prevent the further spread of the virus on the farm. Further tests on other sheep on the farm were negative for the virus.

While this is the first time the Influenza A(H5N1) Virus has been reported in a sheep, it is not the first time influenza of avian origin has been detected in livestock in other countries. There is no evidence to suggest an increased risk to the nation’s livestock population, DEFRA concluded reassuringly.

Still, Influenza A(H5N1) Virus has now succesfully managed to find yet another host and continues to mutate, patiently waiting to infect humans even more.