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.

To learn more about each mosquito-borne disease, find its name below. 
Mosquito

Mosquito-Borne Diseases in Maricopa County 2021

Case numbers are updated every Friday around 9 a.m.

Confirmed and Probable Cases & Deaths as of 10/17/2021

Locally Acquired

DiseaseCurrent Year CasesCurrent Year DeathsCases Same Date Last YearDeaths Same Date Last Year2020 Total Number of Cases
St. Louis Encephalitis (SLE)00626
West Nile Virus (WNV)*46523313
Unspecified Flavivirus (SLE/WNV)†10
202

*The number of WNV cases currently under review and pending classification is 595. This number is not reflected in the number of current cases above.

Travel-Related**

DiseaseCurrent Year CasesCurrent Year DeathsCases Same Date Last YearDeaths Same Date Last Year2020 Total Number of Cases
Chikungunya
00
101
Dengue50
404
Zika00
000

All data are provisional, based on date reported to Public Health.
Maricopa County weekly counts may vary slightly from state reporting due to differences in data reporting.

Current Year = 2021
Last Year = 2020

Disease Statistic Notes 

** Travel-related cases are those in which 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.

Find annual summary numbers of mosquito-borne diseases in Maricopa County, including the number of human deaths attributed to them .

Additional mosquito-borne disease data may be found on the Arizona Department of Health Services’ Mosquito-Borne Disease webpage.

DISEASES

Contact Us

  1. Office of Epidemiology

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    Physical Address
    4041 N Central Avenue
    Phoenix, AZ 85012

    Phone: 602-506-6900
    Fax: 602-372-8935