This indicator tracks the rate of reported West Nile virus disease cases across the United States.
This indicator looks at the incidence of human cases of West Nile virus disease, which reflects the rate of new cases contracted in a given geographic area and time period. Incidence is typically calculated as the number of cases per 100,000 people per year. This indicator focuses on neuroinvasive cases, as the symptoms are noticeable and typically require medical care. The indicator summarizes surveillance data reported to the CDC. West Nile is a nationally notifiable disease, which means health care providers are required to report confirmed cases to their local or state health departments. CDC compiles these reported data and calculates national totals and rates. Figure 1 shows national incidence by year since 2002, when West Nile first became notifiable. Figure 2 shows the incidence for each state, averaged over the period from 2002 to 2014.