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West Nile Virus Activity --- United States, August 4--10, 2004

During August 4--10, a total of 89 cases of human West Nile virus (WNV) illness were reported from 14 states (Alabama, Arizona, California, Florida, Illinois, Kentucky, Louisiana, Minnesota, Mississippi, Missouri, New Mexico, North Dakota, South Dakota, and Wyoming).

During 2004, a total of 24 states have reported a total of 495 cases of human WNV illness to CDC through ArboNET (Table, Figure). Of these, 274 (55%) cases were reported from Arizona. A total of 281 (58%) of the 495 cases occurred in males; the median age of patients was 51 years (range: 1 month--99 years). Illness onset ranged from April 20 to August 3; 10 cases were fatal.

A total of 46 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET in 2004. Of these, 33 (72%) were reported from Arizona, seven from California, three from South Dakota, and one each from Colorado, Iowa, and New Mexico. Of the 46 PVDs, two persons aged 66 and 69 years subsequently had neuroinvasive illness, and seven persons (median age: 55 years; range: 22--72 years) subsequently had West Nile fever.

In addition, during 2004, a total of 2,171 dead corvids and 342 other dead birds with WNV infection have been reported from 35 states. WNV infections have been reported in horses from 24 states (Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, Illinois, Iowa, Kentucky, Minnesota, Mississippi, Missouri, Nevada, New Mexico, North Carolina, Ohio, Oklahoma, South Dakota, Tennessee, Texas, Virginia, Wisconsin, and Wyoming) and in a dog from New Mexico. Two unidentified animal species with WNV infection were reported from Illinois and Nevada. WNV seroconversions have been reported in 336 sentinel chicken flocks from seven states (Arizona, California, Delaware, Florida, Louisiana, Nebraska, and Nevada) and in two wild hatchling birds from Ohio. Three seropositive sentinel horses were reported from Puerto Rico. A total of 2,216 WNV-positive mosquito pools have been reported from 27 states (Arizona, Arkansas, California, Colorado, Connecticut, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Nebraska, Nevada, New Jersey, New Mexico, New York, Ohio, Pennsylvania, South Dakota, Tennessee, Texas, Utah, and Virginia).

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


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