HIV is Human immunodeficiency virus. It is a lentivirus, i.e. a member of retrovirus family which causes AIDS (acquired immunodeficiency syndrome). A condition in humans in which the immune system begins to fail leading to life-threatening opportunistic infections. HIV occurs by transfer of blood, semen, vaginal fluid, pre-ejaculate or breast milk. The four major routes of transmission are unsafe sex, contaminated needles, breast milk, and transmission from an infected mother to her baby at birth.