Susceptibility of an Airborne Common Cold Virus to Relative Humidity

The viability of airborne respiratory viruses varies with ambient relative humidity (RH). Numerous contrasting reports spanning several viruses have failed to identify the mechanism underlying this dependence. We hypothesized that an efflorescence/deliquescence divergent infectivity (EDDI) model accurately predicts the RH-dependent survival of airborne human rhinovirus-16 (HRV-16). We measured the efflorescence and deliquescence RH (RHE and RHD, respectively) of aerosols nebulized from a protein-enriched saline carrier fluid simulating the human respiratory fluid and found the RH range of the aerosols' hygroscopic hysteresis zone (RHE-D) to be 38-68%, which encompasses the preferred RH for indoor air (40-60%). The carrier fluid containing HRV-16 was nebulized into the sub-hysteresis zone (RHD) air, to set the aerosols to the effloresced/solid or deliquesced/liquid state before transitioning the RH into the intermediate hysteresis zone. The surviving fractions (SFs) of the virus were then measured 15 min post nebulization. SFs were also measured for aerosols introduced directly into the RHD zones without transition. SFs for transitioned aerosols in the hysteresis zone were higher for effloresced (0.17 +/- 0.02) than for deliquesced (0.005 +/- 0.005) aerosols. SFs for nontransitioned aerosols in the RHD zones were 0.18 +/- 0.06, 0.05 +/- 0.02, and 0.20 0.05, respectively, revealing a V-shaped SF/RH dependence. The EDDI model's prediction of enhanced survival in the hysteresis zone for effloresced carrier aerosols was confirmed.

Automated summary

The study revealed that the survival of human respiratory viruses in the air is influenced by ambient relative humidity, and successfully predicted this dependence using the EDDI model. The survival rate of the virus in the air was found to be higher in specific ranges of relative humidity, and lower in others.