West Nile Virus Activity --- United States, October 9--15, 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 15, 2003.

During the reporting week of October 9--15, a total of 450 human cases of WNV infection were reported from 27 states (California, Colorado, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Michigan, Minnesota, Mississippi, Montana, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, West Virginia, and Wisconsin), including 13 fatal cases from eight states (Colorado, Georgia, Indiana, Maryland, Michigan, Pennsylvania, Tennessee, and Texas). During the same period, WNV infections were reported in 290 dead birds, 242 mosquito pools, 320 horses, one dog, two squirrels, and three unidentified animal species.

During 2003, a total of 6,957 human cases of WNV infection have been reported from Colorado (n = 2,170), Nebraska (n = 1,108), South Dakota (n = 930), Texas (n = 421), North Dakota (n = 375), Wyoming (n = 320), Montana (n = 214), New Mexico (n = 190), Pennsylvania (n = 183), Minnesota (n = 131), Iowa (n = 128), Louisiana (n = 84), Ohio (n =79), Kansas (n = 76), Mississippi (n = 56), New York (n = 50), Oklahoma (n = 48), Missouri (n = 43), Illinois (n = 39), Florida (n = 32), Indiana (n = 30), Maryland (n = 30), Alabama (n = 29), Georgia (n = 28), North Carolina (n = 21), New Jersey (n = 19), Tennessee (n = 18), Delaware (n = 13), Kentucky (n = 13), Wisconsin (n = 13), Connecticut (n = 12), Massachusetts (n = 12), Virginia (n = 12), Arkansas (n = 11), Michigan (n = four), District of Columbia (n = three), Rhode Island (n = three), New Hampshire (n = two), Arizona (n = one), California (n = one), Nevada (n = one), South Carolina (n = one), Utah (n = one), Vermont (n = one), and West Virginia (n = one) (Figure). Of 6,842 (98%) cases for which demographic data were available, 3,621 (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 10. Of the 6,842 cases, 149 fatal cases were reported from Colorado (n = 44), Nebraska (n = 15), Texas (n = 15), South Dakota (n = eight), Wyoming (n = eight), New York (n = six), Pennsylvania (n = six), Georgia (n = four), Iowa (n = four), Minnesota (n = four), New Mexico (n = four), North Dakota (n = four), Alabama (n = three), Maryland (n = three), Ohio (n = three), Indiana (n = two), Michigan (n = two), Missouri (n = two), Montana (n = two), New Jersey (n = two), Delaware (n = one), Illinois (n = one), Kansas (n = one), Kentucky (n = one), Louisiana (n = one), Mississippi (n = one), Tennessee (n = one), and Virginia (n = one). A total of 668 presumptive West Nile viremic blood donors have been reported to ArboNET. Of these, 590 (88%) 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 521 donors for whom data were completely reported, six subsequently had meningoencephalitis, and 76 subsequently had West Nile fever.

In addition, 10,172 dead birds with WNV infection have been reported from 42 states, the District of Columbia, and New York City; 3,087 WNV infections in horses have been reported from 38 states, 14 WNV infections in dogs, 12 infections in squirrels, and 23 infections in unidentified animal species. During 2003, WNV seroconversions have been reported in 861 sentinel chicken flocks from 14 states. Of the 11 seropositive sentinel horses reported, Minnesota reported seven; South Dakota, three; and West Virginia, one. In addition, seropositivity was reported from one other unidentified animal species. A total of 6,421 WNV-positive mosquito pools have been reported from 38 states, the District of Columbia, and New York City.

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