HIV is the virus that causes the Acquired Immuno Deficiency Syndrome (AIDS). HIV attacks and slowly destroys the immune system by entering and destroying the cells that control and support the immune response system. After a long period of infection, usually 3-7 years, enough of the immune system cells have been destroyed to lead to immune deficiency. The virus can therefore be present in the body for several years before symptoms appear. When a person is immuno deficient, the body has difficulty defending itself against many infections and certain cancers, known as opportunistic infections. It is possible to monitor the development and degree of immuno deficiency, and while the impacts of the disease can be mitigated with proper treatment, there is no cure for AIDS once a person is infected with HIV. There are three main ways in which HIV is transmitted among people: (1) By sexual contact. (2) When infected blood is passed into the body (e.g., through blood transfusion or use of non-sterilized material). (3) From an infected mother to her child during pregnancy, childbirth or breastfeeding (World Bank)