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West Nile Virus Activity --- United States, August 21--27, 2003

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Daylight Time, August 27, 2003.

During the reporting week of August 21--27, a total of 727 human cases of WNV infection were reported from 26 states (Alabama, Arizona, Arkansas, Colorado, Connecticut, Georgia, Illinois, Iowa, Kansas, Maryland, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, and Wyoming), including seven fatal cases from five states (Kansas, Mississippi, Nebraska, New Mexico, and South Dakota). During the same period, WNV infections were reported in 817 dead birds, 207 horses, five unidentified species, and 683 mosquito pools.

During 2003, a total of 1,442 human cases of WNV infection have been reported from Colorado (n = 635), South Dakota (n = 204), Nebraska (n = 190), Texas (n = 106), New Mexico (n = 41), Wyoming (n = 31), Louisiana (n = 30), North Dakota (n = 28), Pennsylvania (n = 27), Mississippi (n = 20), Montana (n = 19), Alabama (n = 14), Kansas (n = 14), Minnesota (n = 13), Oklahoma (n = 12), Iowa (n = 11), Ohio (n = 11), Arkansas (n = five), Florida (n = four), Georgia (n = three), Kentucky (n = three), Tennessee (n = three), Illinois (n = two), Maryland (n = two), Missouri (n = two), New Jersey (n = two), North Carolina (n = two), Virginia (n = two), Arizona (n = one), Connecticut (n = one), Massachusetts (n = one), New York (n = one), South Carolina (n = one), and Wisconsin (n = one) (Figure). Among 750 (52%) cases for which demographic data were available, 419 (56%) occurred among males; the median age was 48 years (range: 3 months--97 years), and the dates of illness onset ranged from March 28 to August 25. Of the 750 cases, 21 fatal cases were reported from Colorado (n = six), Nebraska (n = four), Alabama (n = two), New Mexico (n = two), South Dakota (n = two), Texas (n = two), Kansas (n = one), Mississippi (n = one), and Ohio (n = one). A total of 150 presumptive WNV viremic blood donors have been reported from Nebraska (n = 72), South Dakota (n = 40), Texas (n = 20), New Mexico (n = seven), Mississippi (n = three), Minnesota (n = two), Montana (n = two), Oklahoma (n = two), Florida (n = one), and Louisiana (n = one) . Of these donors, 11 had WNV fever, and none had WNV meningoencephalitis. In addition, 4,222 dead birds with WNV infection were reported from 39 states and New York City; 910 WNV infections in horses have been reported from 32 states, four WNV infections were reported in dogs, one infection in a squirrel, and 10 infections in unidentified animal species. During 2003, WNV seroconversions have been reported in 391 sentinel chicken flocks from 12 states. Louisiana and South Dakota each reported three seropositive sentinel horses. A total of 2,642 WNV-positive mosquito pools have been reported from 32 states and New York City.

Additional information about WNV activity is available from CDC at and


Figure 1
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