West Nile Virus Update --- United States, January 1--November 13, 2007

This report summarizes 2007 West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Standard Time, November 13, 2007. A total of 43 states had reported 3,304 cases of human WNV illness to CDC (Figure, Table). A total of 1,803 (55%) cases for which such data were available occurred in males; median age of patients was 51 years (range: 1 month--97 years). Dates of illness onset ranged from January 8 to November 6; a total of 93 cases were fatal.

A total of 286 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2007. Of these, 46 were reported from California; 40 from Texas; 24 from North Dakota; 21 from South Dakota; 20 from Colorado; 17 from Minnesota; 16 from Oklahoma; 13 each from Arizona, Mississippi, and Montana; 12 from Missouri; eight from Louisiana; seven from Ohio; five each from Iowa, Kentucky, and Utah; four from New Mexico; three each from Puerto Rico and Wyoming; two each from Indiana and Pennsylvania; and one each from Illinois, New York, North Carolina, South Carolina, Tennessee, Virginia, and Wisconsin. Of the 286 PVDs, two persons (median age: 66 years [range: 60--71 years]) subsequently had neuroinvasive illness, and 59 persons (median age: 48 years [range: 16--79 years]) subsequently had West Nile fever.

In addition, 1,599 dead corvids and 473 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 33 states; in four canines in Idaho, Mississippi, and Oregon; in 27 squirrels in California and Oregon; and in three unidentified animal species in Idaho and Montana. WNV seroconversions have been reported in 764 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 7,772 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 http://www.cdc.gov/ncidod/dvbid/westnile/index.htm and at http://westnilemaps.usgs.gov.

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Date last reviewed: 11/14/2007