The UN Food and Agriculture Organisation (FAO) on Monday warned about a new mutant strain of the deadly bird flu H5N1 virus in China and Vietnam. The Rome-based Organisation said it was concerned about the appearance in China and Vietnam of a variant virus able to sidestep the defences provided by existing vaccines, adding that the new strain was known as H5N1 – 2.3.2.1. The FAO said the virus circulation in Vietnam poses a direct threat to Cambodia, Thailand and Malaysia as well as endangering the Korean peninsula and Japan. It warned that the virus could be spread beyond Asia by wild bird migration. The FAO called for heightened readiness and surveillance against a possible major resurgence of the virus, which developed into a pandemic in 2009.