Fig. 1

a Map of Malawi. Background colors reflect topography; the altitude scale is in meters. Blue lines show roads. Cities and towns in Malawi and surrounding countries are shown in red and yellow, respectively. Villages in Malawi are shown in pink, and blue-striped areas represent lakes. b Map showing the sample cluster locations for the Demographic and Health Survey conducted in 2010 in Malawi. Rural locations are shown by black diamonds, urban locations by red diamonds. The three administrative regions in Malawi are color-coded: North (gray), Central (yellow), and South (blue). Black lines mark the boundaries of the 27 districts that were included in the survey. c The population density map for Malawi. The color code shows the number of individuals per square kilometer