West Nile virus--the eye of the storm: a case study.

West Nile virus (WNV) is an arbovirus that emerged in the United States in 1999 and is migrating westward across the country. It occurs in the late summer or fall when there is an abundance of mosquitoes. Symptoms develop 3-14 days after an infected mosquito bites a person. Most WNV infections are asymptomatic or produce mild symptoms; however, 1 in 150 cases is severe with significant neurological deficits. The virus can attack the anterior horn cells, causing acute flaccid paralysis resulting in a poliomyelitis-like syndrome. Diagnosis is based on history, clinical presentation, and laboratory tests. In the late summer or fall, WNV infections should be suspected in persons with unexplained encephalitis, meningitis, or flaccid paralysis. There is no definitive medical treatment for WNV. Preventive measures are the most effective means to combat the disease.