Figure 15.4 Human infections and deaths from West Nile virus in the United States. Following the introduction of the virus to the United States in 1999, the number of human infections and deaths rose rapidly through 2003. Efforts to control mosquito populations, which carry the virus, caused a sharp decline in these effects on humans through 2011. In 2012, however, unusually warm temperatures with high precipitation in some regions of the country resulted in large mosquito populations and a new surge in West Nile infections and deaths. Note that the two y axes have different scales.

Data from http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm#maps.