Influenza transmission in the guinea pig model is insensitive to the ventilation airflow speed: Evidence for the role of aerosolized fomites

Recent experimental work in a guinea pig model has established that influenza A virus is transmissible through the air via aerosolized fomites, which are microscopic dust and dander particulates contaminated with infectious virus [S. Asadi et al., Nat. Commun. 11, 4062 (2020)]. Here we report that influenza A transmits efficiently from intranasally inoculated animals to downwind susceptible animals over a wide range of ventilation airspeeds with no statistically significant change in transmission probability despite increasing the airspeed by a factor of ten. We demonstrate that this finding is inconsistent with a transmission mechanism predicated entirely on emission of virus-laden expiratory particles from the inoculated animal, since the resulting airborne viral concentrations should be greatly diluted at larger airspeeds. Instead, the results suggest that the overall rate of virus aerosolization increases with the ventilation airspeed, in accord with a transmission mechanism predicated on aerosolized fomites in which their generation rate is proportional to the airspeed.