Bird flu outbreaks in the past two weeks in Germany, the Netherlands and Britain could be linked as the virus is most often transmitted through wild birds, said the head of the World Animal Health Organisation (OIE) on Monday.

"Some migrating birds can travel thousands of kilometres," Bernard Vallat told Reuters. "(The virus) could appear anywhere at any time."

However, Vallat stressed that although the H5N8 strain found in Germany earlier this month and in the Netherlands over the weekend can cause severe damage to poultry flocks, it had never been detected in humans.

The H5N8 strain hit Asia severely but had never been reported in Europe before it was detected at a German turkey farm.

It was still unclear whether the outbreak at a duck-breeding farm in northern England involved the H5N8 strain but Britain's chief veterinary officer said it was not the deadly H5N1 strain, which can be transmitted to humans and has caused the death of hundreds of people. – Reuters