HIV/AIDS is caused by the human immunodeficiency virus (HIV) which weakens a person's immune system by destroying important white blood cells, known as CD4 cells or T cells. Over time, HIV can destroy so many of these cells that the body cannot fight off infections and disease, at which point the person is said to have developed AIDS. HIV is most often transmitted via sexual contact with an infected person, sharing needles/syringes with an infected person, or from an infected mother to her child during pregnancy, childbirth or breastfeeding. While treatment cannot cure HIV/AIDS, proper medical care can slow down the damage to the immune system and help infected individuals lead long and productive lives.