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West Nile Virus Update --- United States, January 1--July 24, 2007

This report summarizes 2007 West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, July 24, 2007. A total of 19 states have reported 122 cases of human WNV illness to CDC (Figure, Table). A total of 68 (56%) cases for which such data were available occurred in males; median age of patients was 48 years (range: 15 months--96 years). Dates of illness onset ranged from March 25 to July 18; three cases were fatal.

A total of 23 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2007. Of these, 12 were reported from California; three each from Kentucky and Texas; two from South Dakota; and one each from Iowa, Minnesota, and North Carolina. Of the 23 PVDs, seven persons (median age: 38 years [range: 18--79 years]) subsequently had West Nile fever.

In addition, 310 dead corvids and 98 other dead birds with WNV infection have been reported in 15 states during 2007. WNV infections have been reported in horses in 10 states, in five squirrels in California, and in one unidentified animal species in Idaho. WNV seroconversions have been reported in 75 sentinel chicken flocks in four states (Arizona, California, Florida, and Utah) and Puerto Rico. A total of 646 WNV-positive mosquito pools have been reported.

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


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