Update: West Nile Virus Activity --- United States, 2005

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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, September 27, 2005.

Forty states have reported 1,804 cases of human WNV illness in 2005 (Figure and Table 1). By comparison, in 2004, a total of 1,784 WNV cases had been reported as of September 28, 2004 (Table 2). A total of 935 (56%) of the 1,669 cases for which such data were available occurred in males; the median age of patients was 50 years (range: 3 months--98 years). Date of illness onset ranged from January 2 to September 22; a total of 52 cases were fatal.

A total of 321 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2005. Of these, 86 were reported from California; 52 from Nebraska; 48 from Texas; 22 from Louisiana; 19 from Kansas; 16 from South Dakota; 13 from Arizona; 11 from Iowa; 10 from Minnesota; eight from Illinois; five from New Mexico; four each from Alabama, Pennsylvania, and Utah; three each from Michigan and Oklahoma; two each from Colorado and Mississippi; and one each from Idaho, Montana, Nevada, New York, North Carolina, North Dakota, Ohio, Oregon, and Wisconsin. Of the 321 PVDs, three persons aged 53, 56, and 72 years subsequently had neuroinvasive illness; six persons (median age: 33 years) subsequently had other illnesses; and 71 persons (median age: 46 years [range: 17--78 years]) subsequently had West Nile fever.

In addition, 3,470 dead corvids and 739 other dead birds with WNV infection have been reported from 42 states. WNV infections have been reported in horses from 30 states; four dogs from Idaho, Minnesota, and Nebraska; four squirrels from Arizona; and three unidentified animal species in two states (Arizona and Illinois). WNV seroconversions have been reported in 980 sentinel chicken flocks from 13 states. Eight seropositive sentinel birds have been reported from Michigan. One seropositive sentinel horse was reported from Minnesota. A total of 9,934 WNV-positive mosquito pools have been reported from 39 states (Alabama, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Washington, and Wisconsin) and the District of Columbia.

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