The document discusses the history and impacts of HIV/AIDS in sub-Saharan Africa. It describes how HIV was first identified in Congo in the 1950s and 1980s and spread to the US. By the 1980s it was prevalent in gay communities in cities like San Francisco and Chicago. The virus has crossed species boundaries multiple times, resulting in different subtypes. It attacks CD4 cells in the immune system. While a vaccine is problematic due to HIV's ability to mutate and infect the immune system, about 70% of people with HIV live in South Africa and sub-Saharan Africa, where it has become a major social, economic and political issue.