This year is shaping up to be the worst year ever for West Nile virus (WNV) infections. West Nile virus infection is a vector-borne disease that can cause serious illness, disability, and death. It is transmitted primarily by mosquitoes.
As of August 14, 2012, 693 cases of West Nile virus, including 26 deaths, had been reported to the U.S. Centers for Disease Control and Prevention (CDC). That’s more cases than any year since health officials first detected the virus in 1999. Of the 693 cases, 406 (59%) involved the nervous system (meningitis or encephalitis) and 287 (41%) did not.
Forty-three states reported infections in people, birds, or mosquitoes. More than 80 percent of human cases were reported from six states — Texas, Mississipi, Louisiana, Oklahoma, South Dakota, and California. Almost half came from Texas.
West Nile virus causes severe illness in about 1 out of 150 people. Severe symptoms may include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. Symptoms may last several weeks and permanent neurological damae may occur. About one out of five people experience milder symptoms. But about four out of five people infected with the virus show no symptoms at all.
Source: Centers for Disease Control and Prevention West Nile Virus Page: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm