Bird flu has been found in turkeys at a farm in Tetney near Louth - the first case to be confirmed in the UK.
Most of the 5,000-plus birds at the farm have died and the rest will be humanely culled, officials say.
The farm's location has not been revealed.
Outbreaks of the highly contagious H5N8 strain of avian flu have been reported in Denmark, Sweden, Germany and Finland.
In Holland, 190,000 ducks have been culled in an effort to prevent the spread of the disease.
An investigation into the cause of the outbreak is being carried out by the Department for Environment, Food and Rural Affairs.
A strain of avian flu is currently circling in mainland Europe - leading to the culling of hundreds of thousands of birds - but this is the first case to be confirmed in the UK.
A 3km protection zone and a 10km surveillance zone have been put in place by the around the infected farm to limit the risk of the disease spreading by DEFRA.
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