Fig 1. Location, number of cases, and population at risk when ivermectin distribution began at the study sites: Panel A: Map of the Southern Mexico states showing the three endemic foci for onchocerciasis. Panels B-D: the eighteen sentinel and extra-sentinel communities in Oaxaca (Panel B; prevalence data from 1995), Northern Chiapas (Panel C; prevalence data from 1999), and Southern Chiapas (Panel D; prevalence data from 1995).
