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West Nile Virus Activity --- United States, September 11--17, 2003

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Daylight Time, September 17, 2003.

During the reporting week of September 11--17, a total of 1,214 human cases of WNV infection were reported from 28 states (Alabama, Colorado, Georgia, Iowa, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Dakota, Tennessee, Texas, Wisconsin, and Wyoming), including 26 fatal cases from nine states (Alabama, Colorado, Louisiana, Minnesota, New York, Ohio, South Dakota, Texas, and Wyoming). During the same period, WNV infections were reported in 1,118 dead birds, 355 horses, two dogs, two squirrels, five infections in unidentified animal species, and 638 mosquito pools.

During 2003, a total of 4,137 human cases of WNV infection have been reported from Colorado (n = 1,542), South Dakota (n = 580), Nebraska (n = 543), Wyoming (n = 282), Texas (n = 276), Montana (n = 154), North Dakota (n = 126), New Mexico (n = 124), Pennsylvania (n = 72), Minnesota (n = 57), Louisiana (n = 52), Mississippi (n = 48), Iowa (n = 38), Oklahoma (n = 28), Kansas (n = 23), New York (n = 23), Florida (n = 22), Ohio (n = 22), Alabama (n = 21), Maryland (n = 17), North Carolina (n = 14), Georgia (n = 11), Missouri (n = 10), Illinois (n = eight), Tennessee (n = seven), Indiana (n = six), Kentucky (n = six), Wisconsin (n = six), Arkansas (n = five), New Jersey (n = four), Virginia (n = four), Arizona (n = one), Connecticut (n = one), Massachusetts (n = one), New Hampshire (n = one), Rhode Island (n = one), and South Carolina (n = one) (Figure). Of 3,969 (96%) cases for which demographic data were available, 2,081 (52%) occurred among males; the median age was 47 years (range: 1 month--99 years), and the dates of illness onset ranged from March 28 to September 11. Of the 3,969 cases, 80 fatal cases were reported from Colorado (n = 27), Nebraska (n = 10), South Dakota (n = seven), Texas (n = seven), Wyoming (n = seven), New Mexico (n = four), Alabama (n = three), New York (n = three), Iowa (n = two), Minnesota (n = two), Ohio (n = two), Georgia (n = one), Kansas (n = one), Louisiana (n = one), Mississippi (n = one), Missouri (n = one), and Montana (n = one). A total of 267 presumptive West Nile (WN)--viremic blood donors have been reported from Nebraska (n = 116), South Dakota (n = 56), Texas (n = 20), Wyoming (n = 20), Oklahoma (n = 11), Colorado (n = 10), New Mexico (n = nine), Montana (n = five), Georgia (n = four), Iowa (n = three), Minnesota (n = three), Mississippi (n = three), New Jersey (n = two), Florida (n = one), Illinois (n = one), Louisiana (n = one), Michigan (n = one), and Tennessee (n = one). Of these 267 donors, 34 subsequently had onset of WNV fever, one subsequently had onset of encephalitis, and one subsequently had onset of WNV meningoencephalitis. In addition, 7,263 dead birds with WNV infection were reported from 42 states and New York City; 1,912 WNV infections in horses have been reported from 34 states, 12 WNV infections were reported in dogs, five infections in squirrels, and 17 infections in unidentified animal species. During 2003, WNV seroconversions have been reported in 591 sentinel chicken flocks from 12 states, and 11 seropositive sentinel horses have been reported from four states. A total of 4,412 WNV positive mosquito pools have been reported from 36 states and New York City.

Additional information about WNV activity is available from CDC at and


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