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West Nile Virus Activity --- United States, June 16--22, 2004

As of June 22, 2004, seven states reported a total of 32 human cases of West Nile virus (WNV) illness to CDC through ArboNET. Twenty cases were reported from Arizona, six cases from California, two cases from Florida, and one case each from Nebraska, New Mexico, South Dakota, and Wyoming (Figure). Twenty-three (72%) of the cases occurred in males; the median age of patients was 52 years (range: 9--78 years), and dates of illness onset ranged from May 8 to June 7. Sixteen (50%) of the patients had neuroinvasive WNV illness, 14 (44%) had West Nile fever, and two (6%) had clinically unspecified illness.

A total of 13 presumptive West Nile viremic blood donors have been reported to ArboNET. Of these, 12 were reported from Arizona, and one was reported from New Mexico. Of the 13 donors reported to ArboNET, one person aged 69 years subsequently had neuroinvasive illness, and three persons aged 22, 51, and 52 years had West Nile fever.

In addition, during 2004, a total of 616 dead corvids and 58 other dead birds with WNV infection have been reported from 20 states, and 17 WNV infections in horses have been reported from six states (Alabama, Arizona, Missouri, Oklahoma, Texas, and Virginia). WNV seroconversions have been reported in 65 sentinel chicken flocks from four states (Arizona, California, Florida, and Louisiana). One seropositive sentinel horse was reported from Puerto Rico. A total of 129 WNV-positive mosquito pools have been reported from eight states (Arizona, California, Illinois, Indiana, Louisiana, Missouri, Pennsylvania, and Texas).

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


Figure 1
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