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West Nile Virus Activity --- United States, July 21--27, 2004

During July 21--27, a total of 83 cases of human West Nile virus (WNV) illness were reported from 13 states (Alabama, Arizona, Arkansas, California, Colorado, Florida, Illinois, Iowa, Missouri, New Mexico, Ohio, Pennsylvania, and South Dakota).

During 2004, a total of 265 cases of human West Nile virus illness have been reported through ArboNET from a total of 18 states (Table, Figure). Of these, 161 (61%) cases were reported from Arizona. A total of 143 (56%) of the 265 cases occurred in males; the median age of patients was 50 years (range: 1--85 years). Illness onset ranged from April 23 to July 23; six cases were fatal.

A total of 28 presumptive West Nile viremic blood donors (PVDs) have been reported in 2004 to ArboNET. Of these, 26 (93%) were reported from Arizona, and one each from Iowa and New Mexico. Of the 28 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 1,513 dead corvids and 162 other dead birds with WNV infection have been reported from 32 states. WNV infections in horses have been reported from 16 states (Alabama, Arizona, California, Florida, Idaho, Kentucky, Mississippi, Missouri, Nevada, North Carolina, Oklahoma, South Dakota, Tennessee, Texas, Virginia, and Wyoming) and in a dog from New Mexico. WNV seroconversions have been reported in 209 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 1,030 WNV-positive mosquito pools have been reported from 18 states (Arizona, Arkansas, California, Georgia, Illinois, Indiana, Louisiana, Michigan, Missouri, Nevada, New Jersey, New Mexico, Ohio, Pennsylvania, South Dakota, Tennessee, Texas, and Virginia).

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


Table 1
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Table 1
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