Figure 6. Levels of minimum efforts of intervention strategies needed to control the spread of severe acute respiratory syndrome coronavirus 2, (i.e. reducing the reproductive number to <1), during the coronavirus disease outbreak in China. Strategies considered were quarantine of infected persons and persons who had contact with them (x-axis) and population-level efforts to reduce overall contact rates (y-axis). Percentages denote the percentages of transmissions driven by infected persons that were not detected by surveillance as a result of asymptomatic infection, mild-to-moderate illness or low surveillance intensity.