Mosquito & Vector-Borne Diseases

Even here in the dry climate of Maricopa County, mosquitoes are a problem. Mosquitoes are small insects that breed in standing water and the female mosquitoes need blood to lay eggs. Sometimes mosquitoes carry germs (e.g., viruses and parasites) that can be spread to a person when the mosquito bites them. Preventing mosquitoes from breeding and avoiding mosquito bites are the best ways to avoid getting these diseases.

Mosquito-Borne Diseases in Maricopa County 2018

Confirmed and Probable Cases as of 10/11/2018

DiseaseCurrent Year (2018) as of 10/11/2018Last Year (2017) as of 10/11/20172017 Total Number of Cases
St. Louis Encephalitis (SLE)04
West Nile Virus (WNV)17
Unspecified Flavivirus (SLE/WNV)†012
Unspecified Flavivirus (Dengue/Zika)†022

All data are provisional, based on date reported to Public Health.

Disease Statistic Notes 

* To date, Maricopa County has only experienced travel-related cases of chikungunya, dengue and Zika, meaning that residents brought the disease in from other places or passed on the disease during birth as the result of infection acquired during travel.
† Unspecified Flavivirus indicates an infection that could not be attributed to a single mosquito-borne disease.


Weekly seasonal and annual summary numbers of mosquito-borne diseases, including the number of human deaths attributed to them, can be found here.

Additional mosquito-borne disease data  may be found on the ADHS Mosquito-Borne Disease webpage.