Avian influenza viruses in humans: lessons from past outbreaks

BackgroundHuman infections with avian influenza viruses (AIV) represent a persistent public health threat. The principal risk factor governing human infection with AIV is from direct contact with infected poultry and is primarily observed in Asia and Egypt where live-bird markets are common.Areas of agreementChanging patterns of virus transmission and a lack of obvious disease manifestations in avian species hampers early detection and efficient control of potentially zoonotic AIV.Areas of controversyDespite extensive studies on biological and environmental risk factors, the exact conditions required for cross-species transmission from avian species to humans remain largely unknown.Growing pointsThe development of a universal (‘across-subtype’) influenza vaccine and effective antiviral therapeutics are a priority.Areas timely for developing researchSustained virus surveillance and collection of ecological and physiological parameters from birds in different environments is required to better understand influenza virus ecology and identify risk factors for human infection.