Mosquito-Borne Disease Surveillance

Maricopa County Environmental Services Department has an extensive mosquito-trapping program that enables staff to identify areas where there is mosquito activity and to detect any mosquito-borne diseases. 

Various types of mosquito traps are set up throughout the county that collect mosquitoes for testing. These mosquitoes are pooled together, by species, into groups of 1-50 mosquitoes. This collection of mosquitoes is called a mosquito pool. The female mosquitoes are separated and are then processed and tested for West Nile virus (WNV) and Saint Louis Encephalitis (SLE). Traps with pools or samples that test positive for WNV and SLE are listed in graphics below.

West Nile Virus Statistics


Category
2010201120122013201420152016201720182019
 
2020
 
2021
 
2022*
Positive Dead Birds0020000 0 1 0 0 0 0
Positive Horses0300310 0 2 1 1 4 0
Positive Mosquito Samples
186
9
168
139
218
97
95228138 417 10764
62

Statistics provided by Environmental Services.

*Maricopa County Environmental Services Department's PCR testing results, as of December 22, 2022.

St. Louis Encephalitis Statistics


Category
20152016 2017 2018 2019
 
 2020
 2021
2022*
 
Positive Mosquito Samples600160106 21315244253
         


Statistics provided by Environmental Services.

* MCESD's PCR testing results, as of December 22, 2022

Public Health Statistics on Human Cases

Find current human case counts and historical case counts of mosquito-borne diseases among Maricopa County residents.

  1. Environmental Services Department

    Physical Address
    301 W Jefferson St
    Suite 170
    Phoenix, AZ 85003

    Phone: : 602-506-6616
    Fax: : 602-506-5141

  1. Public Health


    Phone: : 602-506-6900
    Fax: : 602-506-6885