West Nile Virus
2014 End of Year Report
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 2014. Please visit http://www.maricopa.gov/wnv/ for more information about WNV.
Characteristics of Human WNV Infections: Maricopa County, 2014

Non-neuroinvasive†

†

13
3

93

Neuroinvasive†

=Fever
=Fever in donor

43
28
3

Hospitalized

=Encephalitis
=Meningitis
=Other

70
4
2

Deaths

Gender
M/F

12

49/44

=Neuroinvasive
=Non-neuroinvasive
=Unknown severity

60
(0-93)

*Viremic donors who do not become symptomatic (10) are not
included in year total
†Manifestation of disease was not known for 3 cases

Human Cases of WNV in Maricopa County by Month of
Onset, 2010-2014

40
Number of Human Cases1

2014 (n=93)

40
Number of Human Cases

=White, Non-Hispanic
=Hispanic or Latino
=Black, Non-Hispanic
=Asian/Pacific Island
=Other, Non-Hispanic
=Unknown

WNV Cases in Humans and WNV Positive Mosquito Pools in
Maricopa County by Month, 2014

45
2013 (n=52)

35

2012 (n=88)

30

2011 (n=45)
2010 (n=115)

25
20
15

70
Human Cases
(n=93)

35
30

60
50

Mosquito
Pools (n=232)

25

40

20

30

15

20

10

10

5
0

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

10

Month3

5

1

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

A human case is an individual infected with WNV and with a clinically compatible illness
2
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

WNV Deaths in Maricopa County, 2010-2014

TOTAL
Tempe
Surprise
Scottsdale
Phoenix
Peoria
Mesa
Glendale
Gilbert
Chandler

Number of Deaths

Rates of Human WNV Cases in Maricopa County
By City, 2014
1.4
2.38
0.81

City1,3

5.72
1.65
3.69

15

12

6
4

5

2

0
2010

2011

2012

2013

2014

Year
4.34

WNV Mortality Description 2014

2.8
2.00

12

10

1.97
1.7

0.00
1

69
12
1
1
2
8

Number of Mosquito Pools2

Year
Total*

Demographics
Median Age
(Range)
Race/Ethnicity

4.00
6.00
Rates per 100,0002

8.00

Population statistics for each city were obtained from United States Census Bureau
2013 Population Estimates
2
Rate per 100,000 population = (N/population) * 100,000
3
Rates for cities with ≥ 100,000 populations shown
*
Total includes cities displayed in figure, as well as other cities and unincorporated
areas with populations <100,000

Confirmed
Deaths
12

Clinical
Presentation
11
1

=Encephalitis
=Fever

Median
Age
(Range)
78
(62-93)

Gender
M/F
7/5

Race/Ethnicity
10

1
1

=White,
Non-Hispanic or
Latino
=Hispanic or Latino
=Unknown

Mean age of West Nile Virus survivors (54 years) versus deaths (76 years) was statistically
significant for 2014 (α=0.05).