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
 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
 		 2020
 		 2021
 		 2022*
Positive Dead Birds 0 0 2 0 0 0 0  0  1  0  0  0  0
Positive Horses 0 3 0 0 3 1 0  0  2  1  1  4  0
Positive Mosquito Samples
 186
9
 168
 139
 218
 97
 95 228 138  417  10 764
 62
Statistics provided by Environmental Services.
*Maricopa County Environmental Services Department's PCR testing results, as of November 22, 2022.

St. Louis Encephalitis Statistics


Category
 2015 2016  2017  2018  2019
 		  2020
  2021
 2022*
 
Positive Mosquito Samples 60 0 160 106  213 152 44 252
                 

Statistics provided by Environmental Services.
* MCESD's PCR testing results, as of November 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.

Contact Us

  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

    Contact the Department

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

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