Avian influenza (bird flu) H5N1
There are 15 types of avian or bird flu. Most contagious and usually fatal in birds are the strains H5 and H7. Even within the H5N1 strain, variations have been seen throughout the different regions so far affected.
Domestic birds such as chickens and ducks are most at risk from epidemic outbreaks since they tend to live in higher concentrations. Migratory birds transfer the disease between areas, infecting local populations as they go. Recent confirmations of the presence of H5N1 in Turkey, Romania and Greece show the pattern of spread, which is impossible to stop.
Bird Flu has swept through poultry and wild birds in Asia since 2003. So far it has killed large numbers of birds and led to more than 60 human deaths.