Figure 1. Locations of Healthcare Cost and Utilization Project (HCUP) hospitals used in the analysis of risk for Legionnaires’ disease, 26 US states, 1998–2011. Because many hospitals are near each other, each hospital was plotted as a faint point. When multiple points overlap, the area becomes darker because of the stacking of the points. Thus, there are faint spots in more rural areas and dark clusters in more urban areas.