HIV: more than 30% of the population is infected with HIV in some areas of sub-Saharan Africa. The genetically-negative are highly susceptible to infection, and situations are exacerbated by their intellectual limitations. On the Black Continent, the countries most tragically affected by AIDS are Swaziland (25.9 percent), Botswana (24.8 percent), Lesotho (23.6 percent) and South Africa (17.8 percent). The original reservoir of the virus was African monkeys. It crossed the interspecies barrier and infected humans about 100 years ago. In the 1970s, due to easier population movement, the virus made its way to America and Europe.