Environmental Stability of Enveloped Viruses is Impacted by the Initial Size of Droplets
Andrea French, ALEXANDRA LONGEST, Jin Pan, Peter Vikesland, Nisha Duggal, Seema Lakdawala, Linsey Marr,
Virginia Tech Abstract Number: 275
Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept
AbstractRespiratory viruses must maintain stability, or infectivity, in the environment for efficient spread and transmission to occur. Environmental stability can be influenced by many factors, including virion structure, temperature, relative humidity, droplet composition, and fomite surface material. The objective of this study was to determine the effect of size and relative humidity (RH) on viability of respiratory viruses in droplets. We measured the impact of droplet size (volumes of 50, 5, and 1 µL) and RH (40, 65, and 85%) on the stability of two enveloped viruses: bacteriophage Phi6 and influenza A virus. The drying time, or time it took for a droplet to reach quasi-equilibrium or a plateau in mass, ranged from 0.5 hours for a 1 µL droplet at 40% RH to 11 hours for a 50 µL droplet at 85% RH. The macroscale physical characteristics of the droplets at quasi-equilibrium varied with RH but not with the initial droplet volume. We observed more rapid virus decay when the droplets were still wet and undergoing evaporation and slower decay after the droplets had reached quasi-equilibrium. Initial droplet volume had a major effect on virus viability over the first few hours. There was no significant difference in virus decay in 5 µL and 1 µL droplets for H1N1pdm09 at different RHs but there was in the larger 50 µL droplets. Similar observations were confirmed in limited experiments with SARS-CoV-2. Overall, this study suggests that virus decay is closely correlated with the extent of evaporation, which is controlled by RH and is likely a proxy the solute concentrations in the droplet. Taken together, these data suggest that accurate assessment of transmission risk requires the use of physiologically relevant droplet volumes. This is important in considering the applicability of previous studies on virus persistence in large droplet volumes.