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West Nile Virus Update --- United States, January 1--October 16, 2007

This report summarizes 2007 West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, October 16, 2007. A total of 42 states have reported 3,022 cases of human WNV illness to CDC (Table, Figure). A total of 1,646 (55%) cases for which such data were available occurred in males; median age of patients was 51 years (range: 15 months--97 years). Dates of illness onset ranged from January 8 to October 9; a total of 76 cases were fatal.

A total of 265 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2007. Of these, 46 were reported from California; 37 from Texas; 24 from North Dakota; 21 from South Dakota; 20 from Colorado; 17 from Minnesota; 16 from Oklahoma; 13 from Montana; 12 from Mississippi; 11 from Missouri; seven from Arizona; six from Ohio; five each from Iowa and Utah; four each from Kentucky and New Mexico; three each from Puerto Rico and Wyoming; two each from Indiana and Pennsylvania; and one each from Louisiana, New York, North Carolina, South Carolina, Tennessee, Virginia, and Wisconsin. Of the 265 PVDs, two persons (median age: 66 years [range: 60--71 years]) subsequently had neuroinvasive illness, and 52 persons (median age: 48 years [range: 18--79 years]) subsequently had West Nile fever.

In addition, 1,489 dead corvids and 435 other dead birds with WNV infection have been reported in 34 states and New York City during 2007. WNV infections have been reported in horses in 31 states, in three canines in Idaho and Oregon, in 26 squirrels in California and Oregon, and in three unidentified animal species in Idaho and Montana. WNV seroconversions have been reported in 637 sentinel chicken flocks in 11 states (Arizona, Arkansas, California, Delaware, Florida, Iowa, North Carolina, North Dakota, Oregon, Utah, and Virginia) and Puerto Rico. A total of 7,208 WNV-positive mosquito pools have been reported from 36 states, the District of Columbia, and New York City.

Additional information about national WNV activity is available from CDC at and at

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