The most common example of a secondary immune deficiency is the immunodeficiency caused by the human immunodeficiency virus (HIV). HIV attacks certain cells in the immune system and prevents them from carrying out their proper functions against microbes. When the immune system is sufficiently weakened, infected people catch atypical and severe infections. This susceptibility worsens as the disease progresses. According to genetic research reports it has been proved that HIV originated in Africa during the late nineteenth or early twentieth century. The syndrome was first recognized in 1981 by United States Centers for Disease Control and Prevention (CDC). Since its discovery AIDS has caused an estimated 36 million deaths worldwide. The virus is passed from one person to another through blood-to-blood and sexual contact. In addition, infected pregnant women can pass HIV to their babies during pregnancy, delivering the baby during childbirth, and through breast feeding. The treatment of HIV involves medications and vaccines. Two main types of HIV vaccines are currently being tested- preventive and therapeutic. Alternative medicine includes antiretroviral therapies that are available but they do not offer a cure and cause many side effects. HIV /AIDS have had great impact on society. It has had formed a basis of discrimination because of the misconceptions that it can be transmitted by casual non-sexual contact. It has also been a subject to many controversies involving religion.