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 2016. Please visit http://www.maricopa.gov/wnv/ for more information about WNV.
Characteristics of Human WNV Infections: Maricopa County, 2016
Demographics

63

Non-neuroinvasive†
17 Fever

Hospitalized

Deaths

Gender
M/F

45 Neuroinvasive
3 Non-neuroinvasive

5

37/26

Neuroinvasive
22 Encephalitis
23 Meningitis
1 Other

Median Age
(Range)
50
(4-93)

Race/Ethnicity
41 White, Non-Hispanic
2 Black, Non-Hispanic
1 Asian/Pacific Islander
6 Hispanic or Latino
1 Native American
1 Other, Non-Hispanic
11 Unknown

*Viremic donors who do not become symptomatic (3) are
not included in year total

Human Cases of WNV in Maricopa County by
Month of Onset, 2012-2016

WNV Cases in Humans and WNV Positive Mosquito
Pools in Maricopa County by Month, 2016
20

35

Number of Human Cases

30

Number of Human Cases1

2016 (n=63)
2015 (n=62)
2014 (n=93)

25

2013 (n=52)

20

2012 (n=88)

15

15
10

35
30

Human Cases
(n=63)

25

Mosquito
Pools (n=113)

20
15
10

5

5
0

10

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

Number of Mosquito Pools2

Year
Total*

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

Rates of Human WNV Cases in
Maricopa County (MC) By City, 2016
Gilbert
3.23

Surprise

4

6

Tempe

2.72

2012

2.44

Glendale

1.49

Phoenix

0.87

Mesa

0.82

Peoria

0.87
1.49

Population statistics for each city were obtained from United States Census Bureau
2016 Population Estimates
2
Rate per 100,000 population = (N/population) * 100,000
3
Rates for cities with ≥ 100,000 populations shown
*All MC includes cities displayed in figure, as well as other cities and unincorporated
areas with populations <100,000

2013

5

2

3.03

Scottsdale

1

12

3.80

Chandler

All MC*

WNV Deaths in Maricopa 2012-2016

2014

2015

2016

WNV Mortality Description 2016
Confirmed
Deaths
5

Clinical
Presentation
4 Encephalitis
1 Meningitis

Median
Age
(Range)
77
(48-93)

Gender
M/F
1/4

Race/Ethnicity
4 White, Not Hispanic
1 Unknown

Mean age of West Nile Virus survivors (48 years) versus deaths (75 years) was
statistically significant for 2016 (α=0.05).