ABSTRACT
Ethanol (EtOH) effectively inactivates enveloped viruses in vitro, including influenza and SARS-CoV-2. Inhaled EtOH vapor may inhibit viral infection in mammalian respiratory tracts, but this has not yet been demonstrated. Here we report that unexpectedly low EtOH concentrations in solution, approximately 20% (v/v), rapidly inactivate influenza A virus (IAV) at mammalian body temperature (37°C) and are not toxic to lung epithelial cells upon apical exposure. Furthermore, brief exposure to 20% (v/v) EtOH decreases production of infectious progeny viruses in IAV-infected cells. Using an EtOH vapor exposure system that is expected to expose murine respiratory tracts to 20% (v/v) EtOH solution by gas-liquid equilibrium at 37°C, we demonstrate that brief EtOH vapor inhalation twice a day protects mice from lethal IAV respiratory infection by reducing viruses in the lungs without harmful side effects. Our data suggest that EtOH vapor inhalation may provide a versatile therapy against various respiratory viral infectious diseases.