The virus is mainly found in the tropical forests of Central Africa and West Africa. It was first discovered in monkeys in 1958, and in humans in 1970. Between 1970 and 1986, over 400 cases in humans were reported. Small viral outbreaks with a death rate in the range of 10% and a secondary human to human infection rate of about the same amount occur routinely in equatorial Central and West Africa. The primary route of infection is thought to be contact with the infected animals or their bodily fluids. The first reported outbreak outside Africa occurred in 2003 in the Midwestern United States in Illinois, Indiana, and Wisconsin, with one occurrence in New Jersey. No deaths occurred.