West Nile Virus Activity --- United States, September 18--24, 2003

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This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Daylight Time, September 24, 2003.

During the reporting week of September 18--24, a total of 690 human cases of WNV infection were reported from 30 states (Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Iowa, Kansas, Louisiana, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Rhode Island, South Dakota, Texas, Utah, Virginia, Wisconsin, and Wyoming), including 13 fatal cases from 10 states (Iowa, Maryland, Minnesota, Missouri, Nebraska, New Jersey, New York, North Dakota, Ohio, and South Dakota). During the same period, WNV infections were reported in 1,143 dead birds, 231 horses, and 529 mosquito pools.

During 2003, a total of 4,827 human cases of WNV infection have been reported from Colorado (n = 1,542), Nebraska (n = 788), South Dakota (n = 699), Texas (n = 311), Wyoming (n = 302), Montana (n = 187), New Mexico (n = 153), North Dakota (n = 148), Minnesota (n = 79), Pennsylvania (n = 72), Louisiana (n = 67), Iowa (n = 59), Mississippi (n = 51), Ohio (n = 39), Oklahoma (n = 38), New York (n = 37), Florida (n = 32), Kansas (n = 30), Missouri (n = 28), Alabama (n = 26), Illinois (n = 19), Maryland (n = 17), North Carolina (n = 16), Georgia (n = 12), Arkansas (n = 11), New Jersey (n = 10), Wisconsin (n = 10), Tennessee (n = seven), Connecticut (n = six), Indiana (n = six), Kentucky (n = six), Virginia (n = six), Delaware (n = four), Rhode Island (n = three), Arizona (n = one), Massachusetts (n = one), Nevada (n = one), New Hampshire (n = one), South Carolina (n = one), and Utah (n = one) (Figure). Of 4,770 (99%) cases for which demographic data were available, 2,511 (53%) 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 17. Of the 4,770 cases, 93 fatal cases were reported from Colorado (n = 27), Nebraska (n = 13), South Dakota (n = eight), Texas (n = seven), Wyoming (n = seven), New York (n = five), New Mexico (n = four), Alabama (n = three), Iowa (n = three), Minnesota (n = three), Ohio (n = three), Missouri (n = two), Georgia (n = one), Kansas (n = one), Louisiana (n = one), Maryland (n = one), Mississippi (n = one), Montana (n = one), New Jersey (n = one), and North Dakota (n = one). A total of 586 presumptive West Nile viremic blood donors have been reported to ArboNET. Of these, 477 (81%) were reported from the following eight western and midwestern states: Colorado, Kansas, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, and Wyoming. Of the 446 donors for whom complete data are reported, two subsequently developed encephalitis, and 38 subsequently had WNV fever. In addition, 8,406 dead birds with WNV infection were reported from 42 states and New York City; 2,143 WNV infections in horses have been reported from 36 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 603 sentinel chicken flocks from 13 states. Of the 11 seropositive sentinel horses reported, Minnesota repored four, Illinois and South Dakota each reported three, and West Virginia reported one. A total of 4,941 WNV-positive mosquito pools have been reported from 38 states and New York City.

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