The UK has been hit by a record outbreak of avian flu that has led to 500,000 captive birds being culled in recent months. The environment secretary, George Eustice, told the House of Commons: “This year we are now seeing the largest ever outbreak in the UK of avian influenza, with 36 confirmed cases.” He said an avian influenza prevention zone had been declared across the UK at the start of November, requiring strict biosecurity measures and all birds to be kept indoors. He added: “Our chief veterinary officer continues to lead the response to this episode.” Earlier the chief vet, Christine Middlemiss, said she was “very concerned about what’s happening”. Speaking to BBC Radio 4’s Today programme after confirming more outbreaks overnight, she said: “We now have a total of 40 infected premises in the UK – that’s a really high number for the time of year for anything we’ve experienced before.” By comparison, there were 26 outbreaks last winter. Middlemiss said: “All the birds on the premises have to be culled because of the ongoing risk of infection that they pose. The total number is something like half a million will now have been culled.” She said food supplies would not be hit. “That sounds a huge number, and for those keepers affected it is really devastating, but it’s a relatively very small number in terms of egg supply, meat, chicken and so on.” The disease is spread by migratory wild birds from Europe, where high infections levels are also being recorded. A rare white-tailed eagle found dead on Skye is among the wild birds to have tested positive for avian flu, after a postmortem by the pathology unit at Scotland’s Rural College. It is thought to be the first detected avian flu case involving an eagle in Scotland. The adult eagle, from a well-established territory on Trotternish, was found dead on 14 November. Ornithologists believe it may have fed on infected greylag geese. Middlemiss said almost 300 wild birds had been found with the disease at more than 80 locations. There was “a lot of virus out there”, she said. The risk to human health is low but infected birds should not be touched. She said: “It used to be that we would have a reasonable-sized outbreak and then have two or three quiet years. But that’s not happening now. We’re seeing this across the whole of Europe. We need to understand better why we’re getting these ongoing infections every year.” Asked if the disease was still spreading, Middlemiss said: “We’re continuing to get the new detections. I confirmed another two last night and that’s the rate we’ve been going at for the last week or so. We’re seeing this as a huge pressure of infection from our wild birds.” Middlemiss urged people with garden bird feeders to “practice routine hygiene precautions” including proper handwashing. She added: “If you keep chickens and you want to feed wild birds, you need to make sure that everything is completely scrupulously clean and absolutely separate so that you don’t take infection into your own birds and make them sick.” Asked if the climate crisis was to blame for the increased infection, Middlemiss said: “We don’t know specifically, but it’s certainly one of the thoughts that our experts are having. The birds migrate to the north of Russia over the summer and mix with other birds on other global flight pathways and exchange the viruses. So it’s quite plausible that with climate change and change in pathways that different mixing is going on.”