Abstract
Experimental infection of captive Common Terns with Influenza virus A/Tern/South Africa/1961 reproduced the disease seen in the 1961 epizootic during which Tern virus was originally isolated. Infected terns excreted virus in their droppings. At death a viraemia was present but immunofluorescent studies determined the sites at which virus reproduction occurred. A Swift Tern suffered no ill effect from the injection of Tern virus but developed HI antibodies. The role of migrant sea-birds in spreading avian influenza is briefly discussed.