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Abstract An accepted murine analogue for the environmental behavior of human SARS coronaviruses was aerosolized in microdroplets of its culture media and saliva to observe the decay of its airborne infectious potential under relative humidity (RH) conditions relevant to conditioned indoor air. Contained in a dark, 10 m3 chamber maintained at 22°C, murine hepatitis virus (MHV) was entrained in artificial saliva particles that were aerosolized in size distributions that mimic SARS-CoV-2 virus expelled from infected humans’ respiration. As judged by quantitative PCR, more than 95% of the airborne MHV aerosolized was recovered from microdroplets with mean aerodynamic diameters between 0.56 and 5.6 μm. As judged by its half-life, calculated from the median tissue culture infectious dose (TCID50), saliva was protective of airborne murine coronavirus through a RH range recommended for conditioned indoor air (60% < RH < 40%; average half-life = 60 minutes). However, its average half-life doubled to 120 minutes when RH was maintained at 25%. Saliva microaerosol was dominated by carbohydrates, which presented hallmarks of vitrification without efflorescence at low RH. These results suggest that dehydrating carbohydrates can affect the infectious potential coronaviruses exhibit while airborne, significantly extending their persistence under the drier humidity conditions encountered indoors. 

Airborne murine coronavirus was assessed for its sensitivity to the vapors of chemicals commonly used to disinfect indoor surfaces. As a model for the chemical sensitivity of airborne SARS-CoV-2, the infectious potential of airborne Mouse Hepatitis Virus (MHV) was tracked in the presence of the following pure chemical vapors, each of which was below its permissible exposure limit (PEL) as regulated by the US National Institute of Occupational Safety and Health (NIOSH): <50ppmv for glycol; <1ppmv for HOCl; and <1ppmv for H2O2. Along with its growth media, infectious MHV was aerosolized in a particle size distribution between 0.5 l/m and 3.2 l/m into a sealed, dark, 9m3 chamber maintained at 22 C and 60% RH, including levels of chemical vapors maintained below their respective PELs. As judged by the TCID50 of airborne MHV collected by condensation, this airborne virus was rapidly inactivated by HOCl vapor, incurring an average of 99% infectious potential loss after 16 ± 4 min exposure to <0.2 ppmv HOCl. Airborne MHV responded with a 99% loss of infectious potential in 38 ± 10 min of exposure to <0.9ppmv H2O2; and, a 99% loss of infectious potential in 33 ± 15 min when exposed to a gas-phase dipropylene glycol blend <20ppmv as TVOC. The juxtaposition of quantitative RT-PCR and TCID50 responses suggest that even low levels of gas-phase HOCl exposures can damage the genome of airborne coronavirus in relatively short time frames (c.a. < 5 mins).