Fig. 10

Component case totals versus component areas for China and the USA. The regional scale gradient in case distribution in China results in a wider range, and generally lower number, of cases relative to component area compared to USA. The wide range of cases in smaller components in the USA is a result of small components within larger counties with different numbers of cases. As components become larger than individual counties, this effect is reduced and a consistent trend emerges. Nonetheless, even for large components, considerable variability persists because of both intra-component case density gradients and because of different temporal trajectories leading to differences in total number of cases