The United Nations are now warning a possible resurgence, of the deadly avian flu virus, H5N1, saying that there are signs that the mutant strain may be spreading in Asia, including Vietnam and China. According to the Food and Agriculture Organization, current vaccines are incapable of fighting off the variant strain of the H5N1. The World Health Organization (WHO) said that the virus has infected 565 people since it emerged in 2003, causing 331 deaths, and an estimated 20-billion-US-dollar economic loss. With the "unpredictable risks to human health posed by the virus", the Food and Agriculture Organization said that "preparedness and surveillance remain essential" to prevent the reoccurrence of the bird flu outbreak.