Fig. 1

Three health facility catchment areas (HFCAs) in the Lake Kariba region of Southern Province, Zambia, span a range of transmission intensities and population densities. a Village-level prevalence of RDT-positive infections in June 2012 prior to mass drug campaigns shows higher transmission in lakeside areas and lower transmission in higher-altitude villages. Circle size is proportional to village population. b In Bbondo HFCA, households are highly clustered and baseline prevalence is low. c In Luumbo HFCA, households are dispersed and baseline prevalence is high. d In Munyumbwe HFCA, households are predominantly clustered around major roads, and baseline prevalence is mixed, with higher prevalence in the southwest valley and eastern roadside areas