The eyes have it: influenza virus infection beyond the respiratory tract

Avian and human influenza A viruses alike have shown a capacity to use the eye as a portal of entry and cause ocular disease in human beings. However, whereas influenza viruses generally represent a respiratory pathogen and only occasionally cause ocular complications, the H7 virus subtype stands alone in possessing an ocular tropism. Clarifying what confers such non-respiratory tropism to a respiratory virus will permit a greater ability to identify, treat, and prevent zoonotic human infection following ocular exposure to influenza viruses; especially those within the H7 subtype, which continue to cause avian epidemics on many continents.