West Nile Virus Activity --- United States, November 6--12, 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 Standard Time, November 12, 2003.

During the reporting week of November 6--12, a total of 176 human cases of WNV infection were reported from 12 states (Arizona, Georgia, Kansas, Louisiana, Maryland, Nebraska, New Jersey, New Mexico, Pennsylvania, South Dakota, Tennessee, and Virginia), including two fatal cases from Louisiana. During the same period, WNV infections were reported in 39 dead birds, 12 mosquito pools, 93 horses, one cat, and five dogs.

During 2003, a total of 8,393 human cases of WNV infection have been reported from Colorado (n = 2,477), Nebraska (n = 1,698), South Dakota (n = 989), Texas (n = 513), North Dakota (n = 422), Wyoming (n = 339), Pennsylvania (n = 225), Montana (n = 220), New Mexico (n = 201), Minnesota (n = 144), Iowa (n = 143), Ohio (n = 104), Louisiana (n = 103), Kansas (n = 88), Oklahoma (n = 75), New York (n = 67), Mississippi (n = 62), Missouri (n = 59), Maryland (n = 56), Illinois (n = 50), Georgia (n = 41), Alabama (n = 33), Florida (n = 32), Indiana (n = 30), New Jersey (n = 29), North Carolina (n = 24), Tennessee (n = 23), Virginia (n = 23), Arkansas (n = 21), Massachusetts (n = 16), Kentucky (n = 14), Delaware (n = 13), Wisconsin (n = 13), Connecticut (n = 12), Michigan (n = eight), Rhode Island (n = six), Arizona (n = four), District of Columbia (n = three), New Hampshire (n = three), Vermont (n = three), California (n = two), Nevada (n = two), South Carolina (n = one), Utah (n = one), and West Virginia (n = one) (Figure). Of 8,256 (98%) cases for which demographic data were available, 4,251 (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 28. Of the 8,256 cases, 184 fatal cases were reported from Colorado (n = 45), Texas (n = 26), Nebraska (n = 21), South Dakota (n = 13), New York (n = eight), Wyoming (n = eight), Pennsylvania (n = seven), Maryland (n = five), Missouri (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), Louisiana (n = three), Ohio (n = three), Indiana (n = two), Montana (n = two), New Jersey (n = two), Delaware (n = one), Illinois (n = one), Kentucky (n = one), Michigan (n = one), Mississippi (n = one), Tennessee (n = one), and Virginia (n = one). A total of 718 presumptive West Nile viremic blood donors have been reported to ArboNET, including 625 (87%) from the following nine western and midwestern states: Colorado, Kansas, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. Of the 587 donors for whom data were reported completely, six (1%) subsequently had neuroinvasive disease (median age: 45 years; range: 28--76 years), and 90 (15%) had West Nile fever.

In addition, 11,115 dead birds with WNV infection have been reported from 42 states, the District of Columbia, and New York City. WNV infections also have been reported from 41 states in horses (n = 4,084), dogs (n = 26), squirrels (n = 17), cats (n = one), and unidentified animal species (n = 31). During 2003, WNV seroconversions have been reported in 1,377 sentinel chicken flocks from 15 states. Of the 61 seropositive sentinel horses reported, Illinois reported 43, West Virginia reported eight, Minnesota reported seven, and South Dakota reported three. In addition, seropositivity was reported from one other unidentified animal species. A total of 7,602 WNV-positive mosquito pools have been reported from 38 states, the District of Columbia, and New York City.

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