The United Nations' top bird-flu expert says Europe can expect more cases of deadly H5N1 virus in domestic birds over the next few months, after the virus killed 2,500 turkeys in eastern England.

David Nabarro (undated photo)

Dr. David Nabarro says migrating wild birds infected with the virus are likely to come in contact with domestic poultry flocks in Europe, but that the bird-flu threat to humans is very small.

The U.N. official says the virus is unlikely to spread in Britain because authorities reacted quickly to last week's outbreak. Nabarro spoke to reporters Sunday in Indonesia, where he is attending a conference about bird flu.

British officials are enforcing a three-kilometer exclusion zone around the farmm, 210 kilometers northeast of London. They also have slaughtered tens of thousands of healthy turkeys at the same farm as a precaution.

Health experts say it is difficult for humans to contract bird flu from infected birds, but they fear the virus could mutate into a form easily spread by humans, triggering a deadly global pandemic.

A bird-flu outbreak also was reported in Hungary last week.

The World Health Organization said Saturday that bird flu killed a Nigerian woman last month, and Japanese officials report an outbreak among birds on a southern poultry farm. The H5N1 virus has killed 165 people since 2003. Most victims lived in Indonesia.

Some information for this report was provided by AP and Reuters.