Avian flu outbreaks in the past two weeks in the UK, the Netherlands and Germany could be linked, according to the head of the World Animal Health Organisation.
Bernard Vallat said that the virus was most often transmitted through wild birds, which could spread it across countries.
"Some migrating birds can travel thousands of kilometres," Bernard Vallat told Reuters. "(The virus) could appear anywhere at any time."
Vallat said the strain of the H5N8 virus found in Germany and the Netherlands this month can decimate poultry flocks, but there are no recorded cases of the virus infecting a human.
However, the Dutch government said the strain "can be transmitted from animals to humans".
It is unclear whether the strain of the flu found in ducks at a farm in East Yorkshire was H5N8, but Britain's chief veterinary officer has said that it is not the deadly H5N1 strain, that can be transmitted to humans and has killed thousands of people.
The German cases are the first of the strain recorded in Europe. In Asia, the H5N8 strain has severely damaged poultry flocks, with millions of birds slaughtered in South Korea to contain an outbreak.
The European Commission announced this morning that it is discussing the introduction of special protective measures to contain the outbreak in the Netherlands.
Authorities have already begun destroying 150,000 hens at the farm where the virus was found to be present, near the village of Hekendorp.
The Dutch economics ministry though said that the virus could only be spread to humans through very close contact with the infected birds, and has imposed a three-day ban on the transportation of poultry and eggs.
Authorities have set out a 10 kilometer exclusion around the duck farm in Nafferton, Yorkshire. They expect to cull about 6,000 birds, and said there is a high risk that the strain could spread to the wild bird population.