Aerosolization effects on coronavirus infectivity.

Understanding the airborne persistence of coronaviruses is critical for effective infection control, yet the effects of aerosolization and airborne suspension on viral infectivity remain poorly defined. In this study, we used bovine coronavirus (BCoV) as a surrogate for human Betacoronaviruses to evaluate how nebulization, aerosolization time, and continuous air mixing affect virus viability and RNA persistence. BCoV suspensions were aerosolized in a sealed, propeller-mixed chamber using a Collison nebulizer for 5, 10, 15, 30, and 45 min. Aerosols were collected using a Wetted Wall Cyclone (WWC), and post-nebulization suspension from the nebulizer reservoir and original stock were analyzed. Infectivity was quantified by TCID50 assay on MDBK cells, and viral RNA was measured by qRT-PCR. Stock and nebulized suspensions retained stable infectivity, indicating that the mechanical forces of nebulization did not impair viral viability. In contrast, WWC-collected aerosols showed a time-dependent infectivity decline. Viral RNA in aerosols remained comparatively stable, whereas RNA levels in the nebulizer reservoir dropped during the first 5 min of nebulization and then remained constant. Temperature and relative humidity in the chamber during the tests showed only minor fluctuations. These findings showed minimal loss of BCoV viability in suspensions during nebulization and significant inactivation at prolonged air mixing, while RNA levels persist. The pronounced infectivity loss under continuous air mixing highlights the role of mechanical stresses in compromising airborne coronavirus viability, a factor directly relevant to indoor environments where HVAC systems and fans are commonly used. The findings of this study help inform risk mitigation strategies in real-world settings.