Concern is growing among conservationists and nature lovers as the UK’s “largest ever” bird flu outbreak continues to grow.

The RSPB said High Pathogenic Avian Influenza (HPAI) is affecting a range of poultry operations across the UK.

Wild bird species involved are mostly geese, ducks and swans, but a number of birds of prey have also been confirmed to have died.

Around half a million birds have been culled so far, according to UK chief veterinary officer Christine Middlemiss, who said there are 40 infected premises in the UK – 38 in Great Britain including 33 in England.

There has already been a confirmed outbreak at Sennybridge in Powys and Chirk in north Wales – as well as reports of two dead wild birds with bird flu on the Dyfi Estuary.

We have now mapped the outbreak with this interactive map, which shows how the spread has carried around England and Wales.

An Avian Influenza Prevention Zone was declared across the UK on November 3 before being extended on November 29 with the added requirement all captive birds have to be kept indoors, amid concerns that wild birds migrating from mainland Europe during the winter are carrying the disease.

The risk to human health from avian influenza remains very low, according to public health advice, and there is a low food safety risk.

Speaking in the House of Commons, Environment Secretary George Eustice said: “Each year the UK faces a seasonal risk in incursion of avian influenza associated with migratory wild birds.

“While we have that each year, I have to say this year we are now seeing the largest-ever outbreak in the UK of avian influenza with 36 confirmed cases.”

Defra confirmed the most up to date figure is 40 – 33 in England, three in Wales, two in Scotland and two in Northern Ireland.

Dr Middlemiss told the BBC the “phenomenal level” of bird flu has “huge human, animal and trade implications”.

She said the disease is being spread by migratory birds flying back from the north of Russia and eastern Europe.

The vet warned the UK is only a few weeks into a migratory season that goes on until March.

“We are going to need to keep up these levels of heightened biosecurity for all that time,” she said.

The protection zone means that in addition to keeping birds and poultry housed, keepers must continue to take precautions such as regularly cleaning and disinfecting clothing, equipment and vehicles and limiting access to non-essential workers and visitors.

NFU chief poultry adviser Aimee Mahony said it was a “challenging” time for all bird owners.

“Vigilance is key and poultry farmers are doing all they can to ensure the continued health of their flocks, and that their welfare needs are being met,” she said.

“We are relying on all bird keepers, whether they have a small backyard flock or a commercial business, to follow the enhanced biosecurity and housing measures implemented by the chief veterinary officer to help prevent further disease outbreaks.”