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West Nile Virus Activity --- United States, August 18--24, 2004

During August 18--24, a total of 154 cases of human West Nile virus (WNV) illness were reported from 18 states (Alabama, Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Kentucky, Minnesota, Mississippi, Missouri, Nevada, New Mexico, North Carolina, South Dakota, Tennessee, and Wisconsin).

During 2004, a total of 32 states have reported 843 cases of human WNV illness to CDC through ArboNET (Table, Figure). Of these, 304 (36%) cases were reported from Arizona. A total of 469 (56%) of the 843 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 17; a total of 20 cases were fatal.

A total of 77 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET in 2004. Of these, 36 (47%) were reported from Arizona, 16 from California, seven from New Mexico, six from Texas, three each from Florida and South Dakota, two each from Colorado and Wisconsin, and one each from Iowa and Missouri. Of the 77 PVDs, two persons aged 66 and 69 years subsequently had neuroinvasive illness, and 12 persons (median age: 56 years; range: 22--73 years) subsequently had West Nile fever.

In addition, during 2004, a total of 2,961 dead corvids and 514 other dead birds with WNV infection have been reported from 40 states. WNV infections have been reported in horses from 28 states (Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, Illinois, Iowa, Kentucky, Michigan, Minnesota, Mississippi, Missouri, Montana, Nevada, New Mexico, North Carolina, Ohio, Oklahoma, Oregon, South Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin, and Wyoming) and in four dogs from Nevada and New Mexico. Three unidentified animal species with WNV infection were reported from Illinois and Nevada. WNV seroconversions have been reported in 474 sentinel chicken flocks from 11 states (Arizona, Arkansas, California, Delaware, Florida, Iowa, Louisiana, Nebraska, Nevada, South Dakota, and Utah) and in two wild hatchling birds from Ohio. Three seropositive sentinel horses were reported from Puerto Rico. A total of 3,526 WNV-positive mosquito pools have been reported from 31 states (Arizona, Arkansas, California, Colorado, Connecticut, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Montana, 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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Figure 1
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