Virology of Avian Influenza in Relation to Wild Birds

The outbreak of HPAI H5N1 influenza virus in Asia, which spread to Russia, the Middle East, Europe, and Africa, has put increased focus on the role of wild birds in the persistence of influenza viruses. The ecology, epidemiology, genetics, and evolution of influenza viruses cannot be fully understood without taking into account the ecology of their hosts. Here, we review current knowledge on global patterns of low pathogenic influenza virus infections in wild birds, discuss these patterns in the context of host ecology and behavior, and identify gaps in the current knowledge. Potentially important differences between low pathogenic influenza viruses and highly pathogenic H5N1 viruses in wild birds are discussed, in particular with respect to pathogenesis, virus secretion, and host range.