Enhanced aerosol dispersion of a sequential cough and social distancing implications

Sequential coughs, although common, have received less attention in airborne transmission studies compared to single coughs. In this study, we explored aerosol dispersion from sequential coughs using large eddy simulation (LES), validated by particle image velocimetry (PIV) experiments. Two types of sequential coughs were investigated and compared to a single cough: one with two identical peak velocities of 10 m/s (10-10 m/s), and another with peak velocities of 10 m/s followed by 5 m/s (10-5 m/s). In the 10-10 m/s scenario, the second cough merged with the first at 2 s and 1.2 m, resulting in enhanced aerosol dispersion compared to a single cough. In contrast, in the 10-5 m/s scenario, the second cough, due to its lower velocity, caught up with the first at 8 s and 1.6 m. The 10-10 m/s scenario demonstrated a stronger capacity for dispersing aerosols than both the 10-5 m/s scenario and the single cough. Sequential coughs increased infection risk by 2-4 times across the full range and required an average increase of 0.5 m in social distancing, due to the enhanced aerosol dispersion and emission of aerosols. These findings improve our understanding of aerosol transmission and inform social distancing guidelines in indoor environments.