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West Nile Virus Update --- United States, January 1--July 22, 2008

This report summarizes 2008 West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, July 22, 2008. A total of 14 states have reported 43 cases of human WNV illness to CDC (Figure, Table). A total of 26 (54%) cases for which such data were available occurred in males; median age of patients was 46 years (range: 12--80 years). Dates of illness onset ranged from January 17 to July 10; none of the cases were fatal.

A total of eight presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2008. Of these, four were reported from California, three from Louisiana, and one from Kentucky. Of the eight PVDs, one person (aged 47 years) subsequently had West Nile fever.

In addition, 368 dead corvids and 79 other dead birds with WNV infection have been reported in eight states during 2008. WNV infections have been reported in horses in eight states and Puerto Rico, in one squirrel in California, and in one unidentified animal species in Puerto Rico. WNV seroconversions have been reported in 38 sentinel chicken flocks in three states (Arizona, California, and Florida) and Puerto Rico. A total of 975 WNV-positive mosquito pools have been reported from 19 states and New York City.

Additional information about national WNV activity is available from CDC at and at


FIGURE. Areas reporting West Nile virus (WNV) activity — United States, 2008*
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TABLE. Number of human cases of West Nile virus (WNV) illness, by state — United States, 2008*
West Other Total Neuroinvasive Nile clinical/ reported State disease† fever§ unspecified¶ to CDC** Deaths
Alabama 0 1 0 1 0 Arizona 1 0 0 1 0 Arkansas 2 0 0 2 0 California 4 2 0 6 0 Colorado 1 1 0 2 0 Connecticut 0 1 0 1 0 Louisiana 0 2 0 2 0 Mississippi 5 4 0 9 0 North Dakota 0 5 0 5 0 Oklahoma 1 2 0 3 0 South Dakota 0 3 0 3 0 Tennessee 0 1 0 1 0 Texas 24 0 6 0 Utah 01 0 1 0
Total 16 27 0 43 0
* As of July 22, 2008.
† Cases with neurologic manifestations (i.e., West Nile meningitis, West
Nile encephalitis, and West Nile myelitis).
§ Cases with no evidence of neuroinvasion.
¶ Illnesses for which sufficient clinical information was not provided.
** Total number of human cases of WNV illness reported to ArboNET by state and local health departments.
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All MMWR HTML versions of articles are electronic conversions from typeset documents. This conversion might result in character translation or format errors in the HTML version. Users are referred to the electronic PDF version ( and/or the original MMWR paper copy for printable versions of official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices.

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Date last reviewed: 7/23/2008


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