West Nile virus (WNV) arrived in Arizona in 2003 and is now endemic in Maricopa County. The Maricopa County Department
of Public Health (MCDPH) Office of Epidemiology collaborates with the Maricopa County Department of Environmental
Services (MCDES) Office of Vector Control to identify and monitor areas of WNV activity. This report describes trends in
human infections during 2018. Please visit http://www.maricopa.gov/wnv/ for more information about WNV.
Characteristics of Human WNV Infections: Maricopa County, 2018
Demographics
Year
Total*
24

Non-neuroinvasive†
1 Fever

Neuroinvasive
15 Encephalitis
7 Meningitis
1 Other

Hospitalized

Deaths

Gender
M/F

Median Age
(Range)

6

15/9

66
(27-87)

22 Neuroinvasive

Race/Ethnicity
17 White, Non-Hispanic
6 Hispanic or Latino
1 Unknown

*There were 0 viremic blood donors in 2018

WNV Cases in Humans and WNV Positive Mosquito
Pools in Maricopa County by Month, 2018
12

35

Number of Human Cases

30
25
20

Number of Human Cases1

2018 (n=24)
2017 (n=93)
2016 (n=63)
2015 (n=62)
2014 (n=93)

15

10
8
6

70
60

Human Cases
(n=24)

50

Mosquito
Pools (n=140)

40
30

4

20

2

10

0

10

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Number of Mosquito Pools2

Human Cases of WNV in Maricopa County by
Month of Onset, 2014-2018

Month3

5

A human case is an individual infected with WNV and with a clinically compatible illness
Mosquito pools are a collection of mosquitoes collected by MCDES from a county trap and
tested positive for WNV
3
Human data are based on date of symptom onset, mosquito data are based on date of
mosquito collection
1

0

2

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month

In past reports, rates of human WNV illness by
cities were included. Due to the low number of
cases in 2018, this cannot be done. The overall rate
of WNV illness in Maricopa County for 2018 was
0.5 per 100,000 population.

WNV Deaths in Maricopa 2014-2018
12
2

2014

2015

5

6

6

2016

2017

2018

WNV Mortality Description 2018
Confirmed
Deaths
6

https://www.maricopa.gov/2423/Fight-the-Bite

Clinical
Presentation
6 Encephalitis

Median
Age
(Range)
72
(67-87)

Gender
M/F

Race/Ethnicity

3/3

6 White, Not Hispanic

Mean age of West Nile Virus survivors (58 years) versus deaths (74 years) was
statistically significant for 2018 (α=0.05).