Filamentous morphology of influenza A virus confers enhanced stability in aerosols.

Airborne transmission of influenza A virus (IAV) poses significant challenges to public health. However, the mechanisms governing viral inactivation in aerosols remain poorly understood. IAVs exhibit morphological variability, ranging from 100 nm spherical virions to micrometer-long filaments, depending on strain and growth conditions. Although virion morphology was shown to influence transmissibility, the mechanisms of how morphology affects airborne transmission are yet to be delineated. Here, we investigated the impact of virion shape on IAV stability in bulk solutions and an aerosol system with a focus on particles in the submicrometer range to examine how physicochemical aerosol properties, such as elevated solute concentration and low pH, affect infectivity. We show that filamentous viruses exhibit enhanced stability in aerosol particles at 80% relative humidity (RH) and in bulk solution mimicking increased salinity at this RH. Similarly, filamentous viruses exhibited slower decay under acidic conditions, both in bulk solutions and in acidified aerosol particles. Using primary human airway cultures, we further found that filamentous IAVs possess an infectivity advantage under mucosal immune pressures, including neutralizing antibodies and mucus. These results reveal that filamentous shape provides IAV with enhanced stability under diverse environmental conditions in the aerosol phase and increased infectivity in the respiratory epithelium.