A devastating new outbreak of avian flu – which has already wiped out wild bird populations across the UK – is likely to hit Britain in the spring. That is the stark warning made last week by ornithologists who said the disease has now established itself across many parts of the country.

“Wild birds arriving in Britain in a couple of months are very likely to trigger new outbreaks of the disease,” said Claire Smith, senior conservation officer for the RSPB. “A few months ago, I was relatively optimistic about its likely impact this year but outbreaks have continued throughout winter and the outlook for 2023 now looks much grimmer.”

The current bird flu epidemic is caused by the H5N1 strain of virus, which originated in intensive poultry farms in Asia and has since spread round the globe, with infected migrating birds playing a pivotal roll in its spread.

UK egg producers have warned that the future of the premium free range sector is at risk should the eggs lose their prized status because of the ongoing threat of bird flu.

Flocks of free range hens are being housed indoors because of the bird flu outbreak and if they are unable to go back outside by the end of February the eggs will be downgraded to “barn produced”, the British Egg Industry Council (BEIC) has said.

In December the Department for Environment, Food and Rural Affairs (Defra) ordered that all free range hens – providing eggs or meat – be housed to protect against the threat of the H5N8 influenza virus. At that time there were no cases in the UK but there were numerous reports of cases in other European countries. The so-called housing order was for 30 days.

Since then, cases of H5N8 have been found in the UK – on two turkey farms in Lincolnshire and in backyard flocks in Wales and North Yorkshire – as well as in a number of wild birds around the country. The chief veterinary officer, Nigel Gibbens, subsequently extended the housing order until the end of February. Bird flu has since been found in a flock of farmed pheasants in Lancashire.

Concern is now growing among free range producers because the extension will take the housing order to the end of the 12-week period – imposed by the EU – beyond which free range birds will lose their status unless they are allowed outdoors. Mark Williams, the chief executive of the BEIC, is calling for the 12-week cut-off to be extended.