Most humaninfections with avian influenzaA viruses havebeen sporadic andlinked to recent direct contact or close exposure with domestic poultry, including raising backyard poultry or visiting a live poultry market . Contact with dead wild swans (defeathering) was the source of infection for some cases of H5N1 virus infection in Azerbaijan. However, the source of exposure is not always determined for some cases of human infection with avian influenza A viruses. Live avian influenza A viruses have been identified in poultry carcasses sourced in endemic areas. Although cooking destroys virus infectivity, contamination from the carcass before cooking may contribute to some of the cases of zoonotic avian influenza A virus infection with no history of direct exposure to liv epoultry. Virologically confirmed infection with avian-lineage H7N2 virus was identified in an ill veterinarian who had exposure to ill cats. A researcher developed virologically confirmed conjunctivitis with an H7N7 virus that was antigenically related to anavian influenza Avirusafter close exposure to an experimentally infected seal. Infection of the human respiratory tract is likely initiated by inhalation of aerosolized avian influenza A viruses or contact transmission to mucus membranes, including conjunctivae, depending on the specific characteristics of the virus (eg, tropism for receptors with sialic acids attached to galactose by a2,6 linkages primarily in the upper respiratory tract vs sialic acids attached to galactose by a2,3 linkages primarily in the lower respiratory tract), host factors (eg, age, immune function, and underlying comorbidities)andexposure(eg,virusdose,singleormultipleexposures).Someavian influenza A(H7) viruses have tropism for ocular receptors and conjunctivitis has been reported in persons with H7N2, H7N3, and H7N7 virus infections. In regions with enzootic poultry infections, human exposures to avian influenza A viruses such as H5N1, H5N6, and H7N9 has been extensive, but zoonotic disease is stochastic and rare. The reasons for this disconnect between exposure and disease are unclear.