Fig. 1.

Respiratory droplets and aerosols expelled during a sneeze or cough. (a) Droplet formation by a sneeze. The large millimeter-sized, semi-ballistic droplets (green) settle with gravity, while the multiphase cloud/puff comprised of small aerosols (red) propagates over a longer distance. Adapted with permission from [9]. Copyright 2020 Elsevier. (b) A picture of multiphase turbulent gas clouds formed by a human sneeze, obtained with a high-speed camera. It shows that clusters of droplets/aerosols travelled 7–8 m, i.e., up to 26 ft. Adapted with permission from ref. [15]. Copyright 2020 JAMA. (c) Time-dependent path of an emulated, uncovered, heavy cough jet. The jet is composed of vaporized droplets and aerosols, visualized with a green laser. It can be seen that the jet travels up to 12 ft within 53 s. Adapted with permission from [16]. Copyright 2020 American Institute of Physics.