West Nile Virus Activity --- United States, November 20--25, 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 25, 2003.

During the reporting week of November 20--25, a total of 98 human cases of WNV infection were reported from 10 states (Florida, Illinois, Indiana, Michigan, Minnesota, Missouri, Pennsylvania, South Dakota, Tennessee, and Texas), including 10 fatal cases from four states (Florida, Indiana, Missouri, and Texas). During the same period, WNV infections were reported in 137 dead birds, 23 mosquito pools, 41 horses and three dogs.

During 2003, a total of 8,567 human cases of WNV infection have been reported from Colorado (n = 2,477), Nebraska (n = 1,727), South Dakota (n = 1,001), Texas (n = 558), North Dakota (n = 422), Wyoming (n = 339), Pennsylvania (n = 232), Montana (n = 222), New Mexico (n = 202), Minnesota (n = 145), Iowa (n = 142), Ohio (n = 107), Louisiana (n = 105), Kansas (n = 88), Oklahoma (n = 75), New York (n = 67), Florida (n = 65), Mississippi (n = 62), Missouri (n = 61), Maryland (n = 56), Illinois (n = 52), Georgia (n = 42), Indiana (n = 41), Alabama (n = 33), New Jersey (n = 31), Arkansas (n = 25), Tennessee (n = 25), North Carolina (n = 24), Virginia (n = 23), Delaware (n = 16), Massachusetts (n = 16), Michigan (n = 15), Kentucky (n = 14),Wisconsin (n = 13), Connecticut (n = 12), Arizona (n = eight), Rhode Island (n = seven), the District of Columbia (n = three), New Hampshire (n = three), Vermont (n = three), California (n = two), Nevada (n = two), Idaho (n = one), South Carolina (n = one), Utah (n = one), and West Virginia (n = one) (Figure). Of 8,430 (98%) cases for which demographic data were available, 4,462 (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 November 3. Of the 8,430 cases, 199 fatal cases were reported from Colorado (n = 45), Texas (n = 28), Nebraska (n = 21), South Dakota (n = 13), New York (n = eight), Wyoming (n = eight), Pennsylvania (n = seven), Florida (n = six), Missouri (n = six), Maryland (n = five), Georgia (n = four), Indiana (n = four), Iowa (n = four), Kansas (n = four), Louisiana (n = four), Minnesota (n = four), New Mexico (n = four), North Dakota (n = four), Ohio (n = four), Alabama (n = three), Delaware (n = two), Montana (n = two), New Jersey (n = two), Arizona (n = one), Illinois (n = one), Kentucky (n = one), Michigan (n = one), Mississippi (n = one), Tennessee (n = one), and Virginia (n = one). A total of 737 presumptive West Nile viremic blood donors have been reported to ArboNET, including 627 (85%) from the following nine western and midwestern states: Colorado, Kansas, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. Of the 605 donors for whom data were reported completely, six (1%) subsequently had neuroinvasive disease (median age: 45 years; range: 28--76 years), and 98 (16%) had West Nile fever.

In addition, 11,350 dead birds with WNV infection have been reported from 43 states, the District of Columbia, and New York City. WNV infections also have been reported from 41 states in horses (n = 4,146), dogs (n = 30), squirrels (n = 17), cats (n = one), and unidentified animal species (n = 32). 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 7,725 WNV-positive mosquito pools have been reported from 38 states, the District of Columbia, and New York City.

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