The United Nations has warned that avian flu shows signs of a resurgence, while a mutant strain that is able to sidestep vaccines could be spreading in Asia.



The Food and Agriculture Organization (FAO) said the variant has appeared in Vietnam and China and its risk to humans cannot be predicted. There is a threat the virus could spread in Thailand, Malaysia, and Cambodia, where eight people have died after becoming infected this year.



The UN says avian or "bird flu" has killed 331 people since 2003. It has also killed or provoked the culling of more than 400 million domestic poultry worldwide.



The virus had been eliminated from most of the 63 countries infected at its 2006 peak, but remains endemic in Bangladesh, China, Egypt, India, Indonesia, and Vietnam.



The FAO also says the number of cases has been rising again since 2008, apparently because of migratory bird movements.



compiled from agency reports