Aims: There is a lack of consistent explanation regarding the mechanisms by which the airborne virus-laden aerosol composition interacts with RH and influences the viability of embedded viruses. We hypothesized that an Efflorescence/Deliquescence-Divergent-Infectivity model can predict the RH-dependent survival of airborne human-rhinovirus-16 (HRV-16) and influenza A H3N2 virus (IAV H3N2) as the suitable representatives of nonenveloped and enveloped viruses, respectively.
Methods: We used a state-of-the-art technique and measured the efflorescence RH (ERH) and deliquescence RH (DRH) of carrier aerosols nebulized from a protein-enriched saline carrier-fluid simulating human respiratory fluid in term of the major components. RH was then classified into three subclasses based on the hygroscopic behaviours of the carrier aerosols as sub-efflorescence (RH˂ERH), hysteresis (ERH˂RH<DRH) and super-deliquescence (RH˃DRH) zones. We tested the validity of the EDDI model for HRV-16 and IAV H3N2 through two different scenarios. To test the model for nonenveloped HRV-16, the carrier fluid containing the virus was nebulized into the RH<ERH zone or RH>DRH zone air, to set the aerosols to the effloresced/solid or non-effloresced/liquid state before transitioning the RH into ERH˂RH<DRH zone. Following the RH adjustment to the hysteresis zone, the surviving fractions (SFs) of the virus were measured at 15-, 25- and 55-minutes post-nebulization. In the second scenario, aerosols were introduced directly into the RH<ERH, ERH˂RH<DRH and RH>DRH zones without transition and then SFs were measured at 5-, 15- and 45-minutes post-nebulization. We used the same scenarios to test the model for IAV H3N2.
Results: We found SFs for transitioned HRV-16 aerosol in the hysteresis zone after 15 min pos-aerosolization were higher for effloresced (17±2%) than non-effloresced (0.5±0.5%), while these figures for transitioned IAV H3N2 were (9.5±0.8%) and (0.40±0.05%), respectively. SFs for non-transitioned HRV-16 aerosols in the RH<ERH, ERH˂RH<DRH and RH>DRH zones were 18±6%, 5±0.2% and 20±5%, while corresponding SFs for IAV H3N2 aerosols were 12±2%, 2±0.1% and 3±0.4%, respectively.
Discussion: The results revealed that while the SFs of HRV-16 were higher in all investigated RH zones compared to IAV H3N2, both viruses follow a V-shaped SF/RH dependence.
 

Airborne Transmission,Influenza,Rhinovirus,Hospital infection