Gastrointestinal Infiltration in Influenza Virus Infection: Mechanisms and Clinical Insights

Background: Influenza, a primarily respiratory illness, frequently manifests with gastrointestinal (GI) symptoms including nausea, vomiting, diarrhea, and abdominal pain. In this review, we analyze mechanisms describing GI infiltration and subsequent involvement of the GI system during influenza infection. Direct mechanisms involve the presence of viral particles in the GI tract and binding to sialic acid receptor, α2,3 and α2,6 linkages. The influenza virus may gain access to gut tissue via swallowing of respiratory secretions, hematogenous spread, or lymphocytic migration via the lung-gut axis. Indirect mechanisms involve immune system dysregulation via cytokine, interferon, and leukotriene flux, upregulation of consequential apoptotic pathways, or gut microbiome dysbiosis. Together, they promote secondary GI opportunistic infections. These findings improve our knowledge of GI infiltration during influenza infection which may aid in effective clinical diagnosis and treatment, ultimately improving patient outcomes.