Notes from the Field: An Outbreak of West Nile Virus — Arizona, 2019

West Nile virus (WNV), a mosquitoborne flavivirus,* was first identified in the United States in 1999 and first reported in Arizona in 2003 (with 12 human cases); 391 human cases were reported in 2004.Since that time, a median of 103 cases (range = 21-391) have been reported in Arizona annually.† During week 28 in 2019, the Arizona Department of Health Services (ADHS) recorded the highest weekly WNV case count * https://www.cdc.gov/vhf/virus-families/flaviviridae.html