Do migrating wild birds carry H5N1 from country to country?
There is no concrete evidence that migratory birds have helped transmit the disease between countries or regions, but the possibility cannot be ruled out. The spread of H5N1 within and beyond South-east Asia appears attributable to movements of infected poultry. The patterns of spread are not consistent with the timing and direction of movements of wild birds. However, recent outbreaks in Europe have occurred along migratory flyways (including the Danube delta, a great gathering place for migratory waterfowl) during the autumn migration. At present H5N1 has not been isolated from healthy wild birds, only those that were dead or dying. This suggests that it is highly lethal and that most infected birds would not be capable of migration. Avian influenza viruses appear to survive best when temperatures fall below 20ºC. Outbreaks that coincide with southward, autumn migration may represent resurgences of viral transmission in already affected areas as temperatures decline.
