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Update: West Nile Virus Activity --- United States, 2005

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, August 30, 2005.

Thirty-one states have reported 689 cases of human WNV illness (Figure and Table 1) in 2005. By comparison, in 2004, a total of 1,053 WNV cases had been reported, as of August 31, 2004 (Table 2). A total of 367 (57%) of the 640 cases for which such data were available occurred in males; the median age of patients was 50 years (range: 3 months---92 years). Date of illness onset ranged from January 2 through August 24; a total of 16 cases were fatal.

A total of 145 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2005. Of these, 49 were reported from California; 30 from Texas; 22 from Nebraska; 12 from South Dakota; 10 from Louisiana; four from Arizona; two each from Alabama, Colorado, Iowa, Minnesota, Mississippi, and New Mexico; and one each from Illinois, Michigan, North Carolina, North Dakota, Pennsylvania, and Utah. Of the 145 PVDs, two persons aged 53 and 56 years subsequently had neuroinvasive illness, and 35 persons (median age: 46 years [range: 17--77 years]) subsequently had West Nile fever.

In addition, 2,290 dead corvids and 483 other dead birds with WNV infection have been reported from 37 states. WNV infections have been reported in horses from 27 states, three dogs from Minnesota and Nebraska, four squirrels from Arizona, and three unidentified animal species in three states (Arizona, Illinois, and South Dakota). WNV seroconversions have been reported in 540 sentinel chicken flocks from 12 states. One seropositive sentinel horse was reported from Minnesota. A total of 6,290 WNV-positive mosquito pools have been reported from 35 states (Alabama, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, and Wisconsin).

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


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Table 1

Table 1
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Table 2

Table 2
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