Figure 3From: Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USACentroids of census block groups with WNV disease overlain on Iowa population density. The centroids of those census block groups with WNV disease are overlain on a layer of populations density spit into three classes (Low = 0 – 0.5 persons/ha, Medium = 0.5 – 4 persons/ha, and High > 4 person/ha).Back to article page