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West Nile Virus Activity --- United States, October 23--29, 2003

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Standard Time, October 29, 2003.

During the reporting week of October 23--29, a total of 332 human cases of WNV infection were reported from 22 states (Arizona, Georgia, Illinois, Iowa, Kansas, Kentucky, Massachusetts, Minnesota, Montana, Nebraska, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Vermont, and Virginia), including 11 fatal cases from three states (Kansas, Nebraska, and South Dakota). During the same period, WNV infections were reported in 330 dead birds, 450 mosquito pools, 147 horses, and one unidentified animal species.

During 2003, a total of 7,718 human cases of WNV infection have been reported from Colorado (n = 2,170), Nebraska (n = 1,540), South Dakota (n = 964), Texas (n = 470), North Dakota (n = 422), Wyoming (n = 320), Montana (n = 218), Pennsylvania (n = 212), New Mexico (n = 196), Iowa (n = 141), Minnesota (n = 137), Ohio (n = 95), Kansas (n = 85), Louisiana (n = 84), Oklahoma (n = 68), New York (n = 67), Mississippi (n = 56), Illinois (n = 48), Maryland (n = 45), Missouri (n = 43), Georgia (n = 36), Florida (n = 32), Alabama (n = 30), Indiana (n = 30), New Jersey (n = 26), North Carolina (n = 23), Arkansas (n = 21), Virginia (n = 21), Tennessee (n = 20), Massachusetts (n = 17), Kentucky (n = 14), Delaware (n = 13), Wisconsin (n = 13), Connecticut (n = 12), Michigan (n = six), Rhode Island (n = five), Arizona (n = three), District of Columbia (n = three), Vermont (n = three), California (n = two), Nevada (n = two), New Hampshire (n = two), South Carolina (n = one), Utah (n = one), and West Virginia (n = one) (Figure). Of 7,588 (98%) cases for which demographic data were available, 4,012 (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 October 21. Of the 7,588 cases, 166 fatal cases were reported from Colorado (n = 44), Nebraska (n = 20), Texas (n = 17), South Dakota (n = 12), New York (n = eight), Wyoming (n = eight), Pennsylvania (n = six), Maryland (n = five), Georgia (n = four), Iowa (n = four), Kansas (n = four), Minnesota (n = four), New Mexico (n = four), North Dakota (n = four), Alabama (n = three), Ohio (n = three), Indiana (n = two), Missouri (n = two), Montana (n = two), New Jersey (n = two), Delaware (n = one), Illinois (n = one), Kentucky (n = one), Louisiana (n = one), Michigan (n = one), Mississippi (n = one), Tennessee (n = one), and Virginia (n = one). A total of 709 presumptive West Nile viremic blood donors have been reported to ArboNET, including 619 (87%) from the following nine western and midwestern states: Colorado, Kansas, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. Of the 534 donors for whom data are reported completely, six (1%) subsequently had neuroinvasive disease (median age: 45 years [range: 28--76 years]), and 79 (15%) had West Nile fever.

In addition, 10,783 dead birds with WNV infection have been reported from 42 states, the District of Columbia, and New York City; 3,471 WNV infections in horses, 16 WNV infections in dogs, 14 infections in squirrels, and 25 infections in unidentified animal species have been reported from 40 states. During 2003, WNV seroconversions have been reported in 1,287 sentinel chicken flocks from 15 states. Of the 52 seropositive sentinel horses reported, Illinois reported 41, Minnesota, seven; South Dakota, three; and West Virginia, one. In addition, seropositivity was reported from one other unidentified animal species. A total of 7,117 WNV-positive mosquito pools have been reported from 38 states, the District of Columbia, and New York City.

Additional information about WNV activity is available from CDC at and


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