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Why Is West Nile Virus So Bad This Year?

West Nile virus (Flavivirus) was first discovered in Africa and was accidentally introduced to the United States, according to the USDA. The virus is primarily an avian pathogen, transmitted among birds by bird-biting mosquitoes, such as the As

West Nile virus outbreak

The United States is experiencing its worst seasonal outbreak of the mosquito-borne West Nile virus. A total of 3,545 cases, including 147 deaths, were reported in the United States in 2012, the highest human toll by that point in the calendar since the mosquito-borne disease was first detected in the country in 1999.