West Nile virus is a new member or "emergent" to the virus of the family. West Nile Virus is found in both tropical and temperate regions. Because of this it is a dangerous and world-wide killer. The Virus ainly infects birds, but also has the ability to affect humans, horses, and some other mammals. The Virus is spread by bites from infected mosquitoes. In the majority of cases, eight percent, people who are infected with the virus have none of the symptoms. In the other, approximately twenty percent, the virus causes mild symptoms which resemble those of the flu. These symptoms are known as West Nile. The virus is highly capable and able to pass through the blood-brain barrier. The most serious effects of West Nile Virus are encephalitis and meningitis. Both of these diseases can result in death. People that are over the age of fifty are at a greater risk of developing the severe disease. The symptoms of which include nausea, fever, stiff neck and changes in mental status. Symptoms to West Nile Virus will begin to develop three to fifteen days after the initial infection. Currently there is no known effective treatment to the virus. West Nile can be diagnosed by employing an ELISA test which will detect 'IgM antibodies' that develop as a result of the virus. The disease normally starts in an infected bird. A female mosquito will come and bite the infected birds who than carries the virus in her salivary glands. If she bites another bird they will become affected with the virus, and the diease continues to spread in that fashion.