West Nile Virus Activity --- United States, October 2--8, 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, October 8, 2003.

During the reporting week of October 2--8, a total of 646 human cases of WNV infection were reported from 27 states (Alabama, Colorado, Delaware, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Massachusetts, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, South Dakota, Texas, Virginia, Wisconsin, and Wyoming) and the District of Columbia, including 21 fatal cases from 13 states (Colorado, Delaware, Georgia, Illinois, Indiana, Iowa, Kentucky, Minnesota, New Jersey, North Dakota, Pennsylvania, Texas, and Virginia). During the same period, WNV infections were reported in 927 dead birds, 546 mosquito pools, 318 horses, one squirrel, and one unidentified animal species.

During 2003, a total of 6,507 human cases of WNV infection have been reported from Colorado (n = 2,090), Nebraska (n = 1,108), South Dakota (n = 863), Texas (n = 379), Wyoming (n = 320), North Dakota (n = 293), Montana (n = 207), New Mexico (n = 184), Pennsylvania (n = 151), Minnesota (n = 121), Iowa (n = 108), Louisiana (n = 84), Ohio (n = 71), Mississippi (n = 53), Kansas (n = 50), New York (n = 49), Oklahoma (n = 46), Missouri (n = 43), Florida (n = 32), Illinois (n = 30), Alabama (n = 29), Georgia (n = 23), Maryland (n = 20), North Carolina (n = 19), New Jersey (n = 19), Indiana (n = 17), Massachusetts (n = 12), Virginia (n = 12), Arkansas (n = 11), Wisconsin (n = 11), Delaware (n = 10), Kentucky (n = 10), Connecticut (n = nine), Tennessee (n = eight), District of Columbia (n = four), Rhode Island (n = three), New Hampshire (n = two), Arizona (n = one), Michigan (n = one), Nevada (n = one), South Carolina (n = one), Utah (n = one), and Vermont (n = one) (Figure). Of 6,419 (99%) cases for which demographic data were available, 3,383 (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 29. Of the 6,419 cases, 136 fatal cases were reported from Colorado (n = 38), Nebraska (n = 15), Texas (n = 14), South Dakota (n = eight), Wyoming (n = eight), New York (n = six), Pennsylvania (n = five), Iowa (n = four), Minnesota (n = four), New Mexico (n = four), North Dakota (n = four), Alabama (n = three), Georgia (n = three), Ohio (n = three), Maryland (n = two), Missouri (n = two), Montana (n = two), New Jersey (n = two), Delaware (n = one), Illinois (n = one), Indiana (n = one), Kansas (n = one), Kentucky (n = one), Louisiana (n = one), Michigan (n = one), Mississippi (n = one), and Virginia (n = one). A total of 654 presumptive West Nile viremic blood donors have been reported to ArboNET. Of these, 584 (89%) were reported from the following nine western and midwestern states: Colorado, Kansas, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. Of the 510 donors for whom data were completely reported, five subsequently had meningoencephalitis, and 72 subsequently had West Nile fever. In addition, 9,882 dead birds with WNV infection were reported from 42 states, the District of Columbia, and New York City; 2,767 WNV infections in horses have been reported from 38 states, 13 WNV infections were reported in dogs, 10 infections in squirrels, and 20 infections in unidentified animal species. During 2003, WNV seroconversions have been reported in 846 sentinel chicken flocks from 13 states. Of the eight seropositive sentinel horses reported, Minnesota reported four; South Dakota, three; and West Virginia, one. In addition, seropositivity was reported from one other unidentified animal species. A total of 6,179 WNV-positive mosquito pools have been reported from 38 states, the District of Columbia, and New York City.

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