Figure 2From: Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USAMean population density in census block groups with zero to three WNV human disease cases (2002–2006). On the x-axis is the mean population density (persons/ha2) for census block groups calculated according to the number of WNV disease cases (i.e. 0, 1, 2, or 3 cases). The number of census blocks which had that number of cases is shown above the point in the graph.Back to article page