SharecloseShare pageCopy linkAbout sharingImage source, Getty ImagesThe UK’s chief veterinary officer has told the BBC there is a “phenomenal level” of avian flu in the UK.Tens of thousands of farmed birds have already been culled, as the” largest number of premises ever” in an avian influenza outbreak are infected.Officials say the risk to human health is low – there is no link to the Covid-19 pandemic – but infected birds should not be touched.”It has huge human, animal, and trade implications,” the chief vet said.Lessons learned from the foot-and-mouth outbreak are being used to try to control the outbreak, Dr Christine Middlemiss added.As of Wednesday there were 38 confirmed infected premises in the UK – 31 in England, three in Wales, two in Scotland, and two in Northern Ireland. The total last year was 26 confirmed cases. The disease is largely spread by migratory wild birds which return to Britain and pass it on to other birds. Dr Middlemiss said the UK was only a few weeks into the migratory season, which normally goes on until March.”We are going to need to keep up these levels of heightened biosecurity for all that time.” An Avian Influenza Prevention Zone was declared across the UK on 3 November. It was extended on 29 November, requiring all bird owners to keep the animals indoors.Dr Middlemiss said there was a high level of infection in wild birds returning from the north of Russia and the east of Europe, where they spent the summer.The advice from the Department for Environment Food and Rural Affairs (Defra), is that the risk to human health from the avian flu A(H5N1) virus is “very low”. However, members of the public are strongly advised not to touch diseased birds.The availability of eggs in supermarkets is unlikely to be affected, said Dr Middlemiss, because the number of farms affected is low compared to overall egg production.Image source, Getty Images”Whilst we’re happy that there are not going to be any food supply issues, because of the overall large number of chickens and eggs and things we produce, it is devastating for those individual companies involved. It’s also devastating for people who keep yard flocks.”Dead swansThe types of premises infected have ranged from bird sanctuaries and small flocks kept in gardens or yards, up to very large commercial farms. Peregrine falcons, curlews, barnacle geese and herring gulls are some of the wild bird species to have been found dead or dying from the disease.Where a case is confirmed after testing by the Animal and Plant Health Agency (APHA) biosecurity control zones are set up and the infected birds killed. In some commercial farms, more than 10 thousand birds have had to be destroyed. The first detection of the H5N1 strain this season was in rescued swans and captive poultry at a swan sanctuary in Worcester on 15 October.In November dead swans were found around the centre of Stratford-on-Avon and the Diglis Basin in Worcester; footpaths were blocked off and the public urged not to feed the animals. In Belfast the disease was confirmed in wild birds in an urban area. There have been other outbreaks in nature reserves in Scotland.Dr Middlemiss emphasised that “the absolute key” was biosecurity. She said that chicken sheds should be kept “as clean as a surgical theatre”, which would reduce the chance of wild birds either directly or indirectly coming into contact with kept birds.Biosecurity lessonsBiosecurity measures, she said, had been learned from the foot-and-mouth outbreak in 2001 when more than 2,000 cases of the disease in farms across the UK led to the culling of six million cows and sheep. However, foot-and-mouth was spread by cattle-to-cattle contact. Avian flu is being largely spread by wild birds, over which there can be “very little control”.The clinical sign of infection is that birds tend to go off their food and water, then develop respiratory problems, eye discharges and sneezing. Then they can display nervous signs, like twisted necks. Dr Middlemiss said, “We’re not on our own. There are a large number of outbreaks across the EU happening. This is a different strain to last year. We do need to understand why we are seeing more year-on-year outbreaks, and understand what’s behind that. She said she wanted to understand the pattern: “We can’t wait until another year and have an even bigger outbreak. So, we will be working not just with our own scientists but internationally, to understand more of what we can do about what’s behind it.”The RSPB said: “Everyone should take care to maintain good hygiene when feeding garden birds, regularly cleaning feeders outside with mild disinfectant, removing old bird food, spacing out feeders as much as possible, and washing your hands.”Follow Claire on Twitter.