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
2023*
Positive Dead Birds
0
0
2
0
0
0
0
0
1
0
0
0
0
0
Positive Horses
0
3
0
0
3
1
0
0
2
1
1
4
0
0
Positive Mosquito Samples
186
9
168
139
218
97
95
228
138
417
10
764
62
151
Statistics provided by Environmental Services.18
*Maricopa County Environmental Services Department's PCR testing results as of September 22, 2023.
St. Louis Encephalitis Statistics
Category
2015
2016
2017
2018
2019
2020
2021
2022
2023*
Positive Mosquito Samples
60
0
160
106
213
152
44
253
41
Statistics provided by Environmental Services.
* MCESD's PCR testing results as of September 22, 2023.
