Sheep Infected With H5N1 Bird Flu In UK First, Government Testing Confirms

Highly pathogenic H5N1 avian influenza is the virus behind outbreaks of bird flu that have been hitting US farming communities hard since early 2024, as well as wild bird and poultry populations across the world. 

In addition to the marked impact on poultry farming, and the downstream economic hit for consumers, one of the most concerning things about this virus is its ability to jump from birds into mammals. According to the Centers for Disease Control and Prevention (CDC), as of March 18, 989 dairy cattle herds had been impacted across 17 US states. Up to now, spillover events on this scale have not been seen in Europe.

The detection of H5N1 in the milk of a sheep on a farm in England will be a concerning development for authorities, but it’s important to note that at this stage only one animal is known to have been infected. The sheep in question has been humanely culled, the UK Government confirmed in a statement. 

“We have confirmed the detection of influenza of avian origin (H5N1) in a single sheep on a farm in Yorkshire. Strict biosecurity measures have been implemented to prevent the further spread of disease,” said Chief Veterinary Officer Christine Middlemiss.

“While the risk to livestock remains low, I urge all animal owners to ensure scrupulous cleanliness is in place and to report any signs of infection to the Animal Plant Health Agency immediately.”

Given the range of mammal species – including domestic cats – that have been shown to be vulnerable to H5N1 infection, it’s natural to be worried about the risk to humans. In the US, where this virus has been spreading more widely, the CDC has so far confirmed 70 human cases, most of which were associated with direct contact with dairy cows.

Importantly, they say that so far there’s no evidence of human-human transmission. However, three cases in veterinarians sparked some concern when the source of their infection could not be identified, suggesting the disease could have also been spreading silently with few to no symptoms in some cases. 

“Current evidence suggests that the avian influenza viruses we’re seeing circulating around the world do not spread easily to people – and the risk of avian flu to the general public remains very low,” said Dr Meera Chand, Emerging Infection Lead at the UK Health Security Agency (UKHSA). 

Another concern surrounds the food supply – H5N1 has been detected in cow’s milk and now sheep’s milk, as well as beef, although that specific meat never entered the human food supply. Thankfully, as regards the milk, there’s a time-honored way of ensuring that it is safe to drink: pasteurization. And in general, with proper cooking and preparation methods that are required to prevent all foodborne illnesses, H5N1 spread via food is not thought to be a serious risk. 

“Our advice remains that bird flu poses a very low food safety risk to UK consumers since the H5N1 virus is not normally transmitted through food. We continue to monitor the situation closely and will assess any emerging information to continue to ensure UK food is safe,” said Chief Scientific Advisor at the Food Standards Agency Robin May. 

The H5N1 situation – as well as the virus itself – continues to evolve, and health authorities are monitoring developments around the world. That’s why this infection in a sheep was picked up in the first place. 

While people will understandably be worried to hear about the virus making moves into new mammal species in another country, the risk to people is mainly limited to those whose work brings them into close contact with animals, and local health authorities have issued advice on how they can best protect themselves. 

This case underscores the importance of close surveillance and the rapid implementation of biosecurity measures, which are going to continue to be essential to keep bird flu outbreaks under control.