Evidence of Infection with Influenza Viruses in Migratory Waterfowl

Abstract

INFLUENZA A viruses have been isolated from a variety of animal species including several avian species in diverse parts of the world. Some of these avian influenza viruses are closely related antigenically even though they have been isolated from different species, at different times in different countries^1–4. These observations have suggested that migratory birds might be involved in the dissemination of these viruses over vast areas of the world. Except for the isolation of one virus from a severe disease among wild terns in South Africa^5,6, there is no direct evidence that wild birds have been infected with the influenza viruses in the past 10–15 yr. There is mention of fowl plague virus (an influenza A virus) infecting pigeons, ducks and geese, but it is not clear whether this was in natural conditions⁶. Epizootics caused by this virus have been described in several countries^8,9.