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West Nile Virus Activity --- United States, July 14--20, 2004

During the week of July 14--20, a total of 74 cases of human West Nile virus (WNV) illness were reported from seven states (Arizona, California, Florida, New Mexico, New York, South Dakota, and Texas).

During 2004, a total of 12 states have reported a total of 182 cases of human WNV illness to CDC through ArboNET (Table, Figure). Of these, 125 (69%) were reported from Arizona. A total of 94 (54%) of the 182 cases occurred in males; the median age of patients was 51 years (range: 1--84 years); the dates of illness onset ranged from April 23 to July 14; and four cases were fatal.

A total of 23 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET in 2004. Of these, 21 (91%) were reported from Arizona, and one each was reported from Iowa and New Mexico. Of the 23 PVDs, two persons aged 66 and 69 years subsequently had neuroinvasive illness, and five persons (median age: 52 years [range: 22--63 years]) subsequently had West Nile fever.

In addition, during 2004, a total of 1,264 dead corvids and 130 other dead birds with WNV infection have been reported from 31 states, and 39 WNV infections in horses have been reported from 10 states (Alabama, Arizona, California, Idaho, Missouri, North Carolina, Oklahoma, South Dakota, Tennessee, and Texas). WNV seroconversions have been reported in 173 sentinel chicken flocks from four states (Arizona, California, Florida, and Louisiana) and in a wild hatchling bird from Ohio. Three seropositive sentinel horses were reported from Puerto Rico. A total of 591 WNV-positive mosquito pools have been reported from 16 states (Arizona, Arkansas, California, Georgia, Illinois, Indiana, Louisiana, Michigan, Missouri, New Jersey, New Mexico, Ohio, Pennsylvania, Tennessee, Texas, and Virginia).

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


Table 1
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Figure 1

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