MODEL RELEASED. AIDS research. Researcher pipetting a blood sample from a test tube. AIDS (acquired immune deficiency syndrome) is the disease caused by HIV (human immunodeficiency virus), which infects and destroys T-lymphocyte cells, weakening the immune system. Africa has the highest prevalence of HIV/AIDS in the world, accounting for 60% of the total number of people with HIV/AIDS worldwide. Uganda has had the world's most successful response to reducing the spread of HIV so far, falling from 15% prevalence in the early 1990s to around 5% in 2001. Photographed at St. Mary's Hospital in Lacor, Gulu, Uganda.