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West Nile Virus Home > Statistics, Surveillance, and Control >
Statistics, Surveillance, and Control 
Maps and Data | Surveillance Program | Guidelines | Case Definition | See Also

2004 West Nile Virus Activity
in the United States

State
Fatalities
Alabama
15
1
0
16
0
Arizona
214
160
17
391
16
Arkansas
17
10
1
28
0
California
289
395
95
779
28
Colorado
41
250
0
291
4
Connecticut
0
1
0
1
0
District of Columbia
1
1
0
2
0
Florida
33
8
0
41
2
Georgia
14
7
0
21
1
Idaho
1
2
0
3
0
Illinois
29
30
1
60
4
Indiana
8
2
3
13
1
Iowa
13
9
1
23
2
Kansas
18
25
0
43
2
Kentucky
1
6
0
7
0
Louisiana
85
24
0
109
7
Maryland
10
6
0
16
0
Michigan
13
3
0
16
0
Minnesota
13
21
0
34
2
Mississippi
31
18
2
51
4
Missouri
27
9
0
36
2
Montana
2
3
1
6
0
Nebraska
7
46
0
53
0
Nevada
25
19
0
44
0
New Jersey
1
0
0
1
0
New Mexico
31
53
4
88
4
New York
7
3
0
10
0
North Carolina
3
0
0
3
0
North Dakota
2
18
0
20
2
Ohio
11
1
0
12
2
Oklahoma
16
6
0
22
3
Oregon
0
3
0
3
0
Pennsylvania
9
5
1
15
2
South Carolina
0
2
0
2
0
South Dakota
6
45
0
51
1
Tennessee
13
1
0
14
0
Texas
119
57
0
176
8
Utah
6
5
0
11
0
Virginia
4
0
1
5
1
Wisconsin
5
7
0
12
2
Wyoming
2
7
1
10
0
Total  
1142
1269
128
2539
100


West Nile encephalitis and West Nile meningitis are forms of severe disease that affect a person’s nervous system. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord.
Click here for further explanation of WN meningitis and/or encephalitis.



West Nile fever refers to typically less severe cases that show no evidence of neuroinvasion. WN fever is considered a notifiable disease, however the number of cases reported (as with all diseases) may be limited by whether persons affected seek care, whether laboratory diagnosis is ordered and the extent to which cases are reported to health authorities by the diagnosing physician.

Other Clinical includes persons with clinical manifestations other than WN fever, WN encephalitis or WN meningitis, such as acute flaccid paralysis. Clinical/Unspecified cases are those for which sufficient clinical information was not provided.

Total Human Cases Reported to CDC- These numbers reflect both mild and severe human disease cases occurring between January 1, 2004 through December 31, 2004 that have been reported to ArboNET by state and local health departments. ArboNET is the national, electronic surveillance system established by CDC to assist states in tracking West Nile virus and other mosquito-borne viruses. Information regarding 2004 virus/disease activity is posted when such cases are reported to CDC.

Of the 2539 cases, 1142 (45%) were reported as West Nile meningitis or encephalitis (neuroinvasive disease), 1269 (50%) were reported as West Nile fever (milder disease), and 128 (5%) were clinically Clinical/Unspecified at this time. Please refer to state health department web sites for further details regarding state case totals.

Note: The high proportion of neuroinvasive disease cases among reported cases of West Nile virus disease reflects surveillance reporting bias. Serious cases are more likely to be reported than mild cases. Also, the surveillance system is not designed to detect asymptomatic infections. Data from population-based surveys indicate that among all people who become infected with West Nile virus (including people with asymptomatic infections) less than 1% will develop severe neuroinvasive disease. See: Mostashari F, Bunning ML, Kitsutani PT, et al. Epidemic West Nile Encephalitis, New York, 1999: Results of a household-based seroepidemiological survey. Lancet 2001;358:261-264.

For Case Information:
1999|2000|2001|2002|2003|2004|2005|2006|2007|2008


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