ADHS Office of Infectious Disease Services published a report last week in the CDC Morbidity and Mortality Weekly Report describing concurrent outbreaks of West Nile virus and St. Louis encephalitis virus disease in Arizona. These outbreaks occurred from May through October this year, and resulted in over 100 illnesses . Co-outbreaks of these two diseases have not been documented before in the United States, and Arizona was the only state to report any human cases of St. Louis encephalitis this year.
Both West Nile virus and St. Louis encephalitis virus are primarily spread by the bite of mosquitoes, and can cause symptoms ranging from fever, headache, and body aches to encephalitis or meningitis. As part of the investigation, ADHS and Maricopa County Department of Public Health staff helped provide education to 19 healthcare facilities to increase awareness of the outbreaks and provide testing recommendations for West Nile virus and St. Louis encephalitis virus. ADHS also worked with local vector control agencies around the state to enhance mosquito trapping and testing efforts. The CDC also participated in the investigations through assistance with pesticide resistance trials, bird testing, and state-wide mosquito control training.
Both outbreaks ended in late October, but it is important to prevent mosquito bites year-round. To protect yourself from mosquitoes, you can wear lightweight long-sleeved clothing, use insect repellent, and reduce mosquito breeding sites by dumping standing water around your home. You can learn more about mosquitoes and the diseases they carry on our website.