Highly virulent variants of avian flu now appear endemic in wild birds, making farms prone to outbreaks all year, experts warn

Free-range chickens and eggs may no longer be feasible to produce in the UK and elsewhere in Europe in future due to a dramatic escalation in avian flu outbreaks, say leading disease experts. The UK and continental Europe have been hit by the largest outbreak of avian flu on record this winter, with millions of birds culled on farms across the continent.

Experts say highly pathogenic variants of avian flu now appear to be endemic in wild birds, creating a risk of infection all year. In the UK, farmers have been ordered to keep their birds indoors since last November and as of this week have been prevented from selling their eggs as free range.

Barn Eggs from birds in indoor housing of one or more levels that are free to move around. There is a maximum stocking density of nine hens per square metre of useable area. 

Cage Eggs from birds housed indoors in cages, with each one holding between 40 and 80 hens and including a nest box and perches.

Organic Birds that lay these eggs have daytime access to an outdoor area. Indoors there is a maximum stocking density of six hens per square metre of useable area. They are also held in smaller flocks and fed an organically produced diet.

Free-range Eggs from birds with daytime access to an outdoor area. The indoor housing has a maximum stocking density of nine hens per square metre of useable area.

The latest reported outbreak, at a farm in Suffolk last weekend, led to more than 80,000 ducks being culled after confirmation of a highly pathogenic variant of avian flu. “There is a serious problem for free-range and outdoor farms,” said Dr Guillaume Fournié, a veterinarian and epidemiologist at the Royal Veterinary College.

“We are seeing outbreaks on large [indoor] poultry farms that would have had high biosecurity. This suggests that with high environmental exposure to the virus, now it’s hard to ensure a farm is 100% biosecure.”

Marion Koopmans, a virologist and adviser to the World Health Organization (WHO), said the situation was “horrible” for the free-range poultry industry.

“The ecology [of avian flu] has changed drastically in just a few years. We now have local circulation all year round in Europe, it’s not just a seasonal threat. It has a permanent presence in the wild bird population.” Highly pathogenic avian flu is already endemic in a number of countries in Asia, with infection of poultry reported all-year round. “The question [in the UK/Europe] is whether sedentary (non-migratory) wild birds will maintain the virus circulation over the summer. This would mean a constant pressure of infection on poultry farms, which would then increase seasonally with migratory birds,” said Fournié. Koopmans, who took part in the WHO’s Covid mission to China in 2021, said higher levels of biosecurity, vaccination of chickens and reductions in intensive poultry farms in parts of Europe may all be needed to prevent outbreaks. Measures to ensure biosecurity and prevent infection reaching hens include cleaning and disinfecting, safe storage of feed and water and quarantining new stock.

France, which has experienced close to 1,000 avian flu outbreaks this winter, has been trialling avian influenza vaccines, but the solution has been complicated by the numerous variants of avian flu. The market for free-range eggs has grown rapidly in the UK over the past decade. Last year, almost two-thirds of 11 billion eggs produced in the UK last year were free-range – up from 27% in 2004. The Co-op, Sainsburys, M&S, Morrisons and Waitrose no longer stock eggs that are not free-range.

Some have suggested introducing covered outdoor areas or changing the rules for free-range egg producers to allow for longer periods spent indoors.

However, it is unclear how consumers would react to this shift. “The whole point of free-range is they have the opportunity to roam outside,” said Andrew Knight, a veterinary professor at the University of Winchester. Radically changing the rules for free-range eggs would be wrong, said Dan Crossley, from the Food Ethics Council. “I think most people have a reasonable understanding of what free-range is, so what we want to avoid is muddying the water and any confusion around what different terms mean.”

UK government officials have said there are no plans to review the existing legislation, which provided producers with a 16-week “derogation” during which the free-range description can be kept on eggs even though the hens have been confined. Mark Williams, chief executive of the British Egg Industry Council, said he was confident that hens would be allowed outside again soon. “The greatest risk comes when the migratory birds are carrying it around, which is why we have these outbreaks at the same time every year between Autumn and Spring,” he said. The UK Health Security Agency said there was year-round avian flu surveillance of dead wild birds. “Despite recording a record number of outbreaks this season, the risk to the wider public from avian flu continues to be very low,” said a spokesperson. Transmission from an infected bird to a human is very rare, according to health officials, with fewer than five cases recorded in the UK – most recently in January, when a man caught it from ducks he kept inside his home.

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