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West Nile Virus Update --- United States, January 1--September 11, 2007

This report summarizes 2007 West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, September 11, 2007. A total of 38 states have reported 1,395 cases of human WNV illness to CDC (Figure, Table). A total of 770 (56%) cases for which such data were available occurred in males; median age of patients was 49 years (range: 15 months--96 years). Dates of illness onset ranged from January 8 to September 7; a total of 38 cases were fatal.

A total of 136 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2007. Of these, 33 were reported from California; 20 from Texas; 13 from Oklahoma; 11 from South Dakota; nine from Minnesota; seven each from Missouri and North Dakota; five from Colorado; four from Kentucky and Mississippi; three each from Iowa, Nebraska, New Mexico, Puerto Rico, and Utah; and one each from Arizona, Louisiana, Montana, North Carolina, Pennsylvania, South Carolina, Virginia, and Wyoming. Of the 136 PVDs, two persons (median age: 66 years; range: 60--71 years) subsequently had neuroinvasive illness, and 31 persons (median age: 49 years; range: 18--79 years) subsequently had West Nile fever.

In addition, 951 dead corvids and 292 other dead birds with WNV infection have been reported in 29 states and New York City during 2007. WNV infections have been reported in horses in 26 states, one canine in Oregon, 11 squirrels in California, and three unidentified animal species in Idaho and Montana. WNV seroconversions have been reported in 316 sentinel chicken flocks in nine states (Arizona, Arkansas, California, Delaware, Florida, Iowa, North Dakota, Oregon, and Utah) and Puerto Rico. A total of 5,172 WNV-positive mosquito pools have been reported from 35 states and New York City.

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


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