Fig. 4: Inferred statistics of transmission bottleneck sizes given changes in the effective viral load.

Statistics were calculated from an ensemble of 10⁶ simulations for each combination of environment and effective viral load. Lines connect points calculated at different viral loads. The dashed vertical black line shows the mean number of plaque-forming units at the peak of SARS-CoV-2 infection, while the grey shaded area shows a 95% confidence interval for this statistic³⁵. The solid vertical black line shows the effective viral load as specified in the default parameters of our model. Statistics are shown describing (a). The proportion of transmissions with bottleneck size 1. b The proportion of transmissions with bottleneck size 10 or less. c The expected number of people infected in each environment, R_env. Horizontal dashed lines in this figure indicate limit values for each environment, as would occur given a theoretically infinite effective viral load.