AIDS (Acquired immune deficiency syndrome or acquired immunodeficiency syndrome) is a disease caused by a virus called HIV (Human Immunodeficiency Virus). The illness alters the immune system, making people much more vulnerable to infections and diseases. This susceptibility worsens as the disease progresses.

HIV is found in the body fluids of an infected person (semen and vaginal fluids, blood and breast milk). 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.

HIV can be transmitted in many ways, such as vaginal, oral sex, anal sex, blood transfusion, and contaminated hypodermic needles.

Both the virus and the disease are often referred to together as HIV/AIDS. People with HIV have what is called HIV infection. As a result, some will then develop AIDS. The development of numerous opportunistic infections in an AIDS patient can ultimately lead to death. 

According to research, the origins of HIV date back to the late nineteenth or early twentieth century in west-central Africa. AIDS and its cause, HIV, were first identified and recognized in the early 1980s. 

There is currently no cure for HIV/AIDS. Treatments can slow the course of the disease - some infected people can live a long and relatively healthy life.

The HIV virus (AIDS virus) weakens the body's immune system. It is spread through sexual contact, needle sharing, or from an infected mother to baby. There may be no symptoms for years, but a blood test can tell if you have been infected. With appropriate treatment, many serious illnesses can be prevented. Some people have flu-like symptoms 1 to 2 months after they become infected, like swollen lymph nodes, fever, and headaches.

Update September 25th, 2013 - UNAIDS reported that since 2001, the number of HIV infections among children fell by 52% worldwide, and by 33% among adults and children combined.