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

Abstract

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.

Figure. Detection of H7 subtype influenza viruses in avian species

Outbreaks of H7 subtype highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI) in avian species reported to the World Animal Health Information Database and the World Organization for Animal Health since 2005 and 2006, respectively; detailed outbreak reports can be located from these sources. Neuraminidase subtype paired with H7 haemagglutinin is shown. Norway, Portugal, Vietnam, and France reported presumed or confirmed H7 subtype outbreaks of low avian pathogenicity in the absence of neuraminidase determination.