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West Nile Virus
Source: Centers for Disease Control and Prevention
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The spread of the West Nile virus/encephalitis in the United States is a major health concern. The virus was discovered in Uganda in 1937. Though the first reported case was in New York in 1999, it could have started before 1999 in any state that borders NY if cases were not reported by lack of knowledge. It is a mosquito-borne disease that has spread across the United States. It has killed 284 people in 2002.
Encephalitis is an inflammation of the brain and can be caused by viruses and bacteria, including viruses transmitted by mosquito bites. West Nile encephalitis is caused by the West Nile virus, a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to the St. Louis encephalitis virus found in the United States.
Transmission is a vicious circle. Mosquitoes become infected when they feed on infected birds. The virus gets into the mosquito's salivary glands. Then the mosquito bites a human or an animal, injecting the virus, which can multiply and cause illness.
Symptoms vary depending on the severity of the infection.