The overall incidence rate for the state was 7.8 cases per 100,000 population. Almost half of the cases were reported from the northeastern quadrant of the state, including the Dallas/Fort Worth metroplex (902 [48%] cases): Dallas (396 [21%]), Tarrant (259 [14%]), Collin (64 [3%]), and Denton (183 [10%]) counties. These 4 counties had a combined incidence rate of 16 cases per 100,000 population. Cases Sources: Final Cumulative Maps & Data for 1999–2018, Preliminary Maps & Data for 2019, and West Nile Virus Disease Cases by State 2020, Centers for Disease Control and Prevention *2019 also had 104 presumptive cases observed in blood donors ** as of December 15, 2020, also 127 presumptive cases observed in blood donors Maps of progression The following maps show the progress of human cases of West Nile across the United States. States are colored according to the percentage of all U.S. West Nile cases they represented in that year. Zero percent (no cases) is colored white; less than 1% is blue; between 1% and 5% is green; between 5% and 10% is yellow, and greater than 10% of cases in a year is red. Counties of reported cases by year References CDC West Nile Virus Statistics, Surveillance, and Control West Nile Cases Drop as Immunities Emerge, Experts Say CDC Information Page For Current Cases and Deaths For West Nile Virus History of science and technology in the United States Diseases and disorders in the United States Flaviviruses