Quantifying the stability of influenza virus during evaporation and suspension phases using a novel bioaerosol...

Understanding the inactivation kinetics of airborne influenza viruses is essential for accurately assessing infection risk and developing effective ambient control strategies. However, most existing studies focus on virus stability during the aerosol suspension phase, with limited quantitative data on the critical evaporation phase immediately after droplet release. Here, we developed a novel controllable relative humidity (RH), temperature, and particle size aerosol quantification experimental system, using H1N1 and H3N2 influenza viruses to quantify the inactivation rate. The mixing tube outlet achieved droplet evaporation equilibrium at specific temperature and RH (±0.5°C, ±1.5% RH); the inertial impactor enabled particle size selection; the aerosol remained suspended within the rotating drum maintaining ±0.3°C and ±2% RH stability. Results indicated that at 25°C, influenza virus survival during the evaporation phase exhibited a U-shaped relationship, with H3N2 showing higher sensitivity than H1N1; however, at 35°C, the viability of influenza viruses increased with rising RH. Notably, the inactivation rate constants of H1N1 influenza viruses during evaporation exceeded those in the suspension phase by two orders of magnitude, providing the first kinetic quantification of this rapid inactivation process. These findings demonstrate that virus inactivation during the evaporation phase is a dominant yet previously underestimated pathway and establish a new bioaerosol experimental system for quantifying the stability of airborne pathogens under controlled ambient conditions.