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West Nile Virus Activity --- United States, August 11--17, 2004

During August 11--17, a total of 194 cases of human West Nile virus (WNV) illness were reported from 17 states (Alabama, Arizona, California, Colorado, Florida, Illinois, Louisiana, Maryland, Minnesota, Mississippi, Missouri, New Mexico, Ohio, South Dakota, Texas, Utah, and Virginia).

During 2004, a total of 27 states have reported 689 cases of human WNV illness to CDC through ArboNET (Table, Figure). Of these, 291 (42%) cases were reported from Arizona. A total of 386 (56%) of the 689 cases occurred in males; the median age of patients was 50 years (range: 1 month--99 years). Illness onset ranged from April 23 to August 12; a total of 20 cases were fatal.

A total of 55 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET in 2004. Of these, 33 (60%) were reported from Arizona, eight from California, three each from Florida, New Mexico, and South Dakota, two from Colorado, and one each from Iowa, Missouri, and Wisconsin. Of the 55 PVDs, two persons aged 66 and 69 years subsequently had neuroinvasive illness, and 11 persons (median age: 55 years [range: 22--73 years]) subsequently had West Nile fever.

In addition, during 2004, a total of 2,530 dead corvids and 441 other dead birds with WNV infection have been reported from 36 states. WNV infections have been reported in horses from 25 states (Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, Illinois, Iowa, Kentucky, Michigan, Minnesota, Mississippi, Missouri, Nevada, New Mexico, North Carolina, Ohio, Oklahoma, South Dakota, Tennessee, Texas, Virginia, Wisconsin, and Wyoming) and in one dog each from Nevada and New Mexico. Two unidentified animal species with WNV infection were reported from Illinois and Nevada. WNV seroconversions have been reported in 393 sentinel chicken flocks from eight states (Arizona, California, Delaware, Florida, Louisiana, Nebraska, Nevada, and Utah) and in two wild hatchling birds from Ohio. Three seropositive sentinel horses were reported from Puerto Rico. A total of 3,109 WNV-positive mosquito pools have been reported from 30 states (Arizona, Arkansas, California, Colorado, Connecticut, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Nebraska, Nevada, New Jersey, New Mexico, New York, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Virginia, and Wisconsin).

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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