Doubts hang over source of bird flu spread

[摘要] The H5N1 avian influenza virus has spread to Africa and the European Union for the first time. Attention is focused on controlling the outbreaks, but, scientists are also urgently trying to confirm the cause of the virus's geographical spread. Although migratory birds have been widely blamed, some believe that the risks posed by the poultry trade are being overlooked. It is difficult to be sure whether migratory birds are sparking new outbreaks in poultry, or whether they pick up the virus from poultry infected by other routes. Countries with strict bans on poultry imports from neighbouring infected countries, such as Myanmar, South Korea and Malaysia, are currently free of the disease.