Bird flu has been found at a farm in Lincolnshire, the Department for Environment, Food and Rural Affairs (Defra) has confirmed.
More than 5,000 turkeys at the farm in Louth have been diagnosed with the H5N8 strain of avian flu, Defra said.
Most of the birds have died and the remaining are due to be culled.
Public Health England (PHE) said the risk to humans was “very low”. A 1.8 mile (3km) protection zone has been set up around the farm.
Defra said it has also set up a six mile (10km) surveillance area to reduce the risk of the disease spreading.
A PHE spokesman said: “We continue to work closely with Defra throughout this investigation.
“Despite the risk being very low, we will offer health advice to those people who may have been exposed on the farm as a precaution.”
Analysis: By James Gallagher, health and science reporter, BBC News
This is a threat to flocks not people, so if you’re not a poultry farmer, don’t worry.
The bird flu virus comes in different strains and this one – H5N8 – has been circulating in wild birds in Asia since 2010.
This is now the second time it has caused outbreaks in Europe after the autumn migration.
But while H5N8 is good at infecting birds, it’s pretty rubbish at making the leap into people.
Bird flus are intensely monitored and there has not been a single reported case of H5N8 infecting people anywhere in the world.
There will always be a tiny theoretical risk but this will be contained to those handling the birds.
Chief Veterinary Officer Nigel Gibbens said it was “the same strain that has been affecting poultry in Europe”.
“Bird keepers should remain alert for any signs of disease, report suspected disease immediately and ensure they are maintaining good bio-security on their premises,” he said.
“We are urgently looking for any evidence of disease spread associated with this strain to control and eliminate it.”
An investigation is under way to establish the source of the outbreak, which was not likely to cause “any impact on the supplies of turkeys or other birds over Christmas”, Defra said.
Last week, the government told owners to keep birds indoors for 30 days to protect them from the highly-infectious strain of avian flu.
The H5N8 bird flu strain has been found in poultry and wild birds in 14 European countries including Germany and France.