AIDS (Acquired Immune deficiency syndrome) is a disease caused by a virus called HIV. HIV stands for Human Immunodeficiency Virus. HIV infection is a serious condition in the world today. World Health Organization (WHO) has considered AIDS a Pandemic (epidemic across a very large region) disease.

As the name suggests, the HIV virus leads to a deficiency of immunity in humans. That, in turn, leads to a range of disease conditions, primarily due to seriously impaired immunity due to the invasion of the virus. AIDS leads to a decrease in the body's self-healing mechanism and many opportunistic infections like Tuberculosis, Pneumonia, fungal infection; diarrhea, etc. affect the body.

From 1981 to 2006 over 25 million people died due to HIV infection. About 0.26 million children have died of AIDS in 2009. An estimated 0.6% world population suffers from AIDS.

The causative organism of AIDS is the HIV virus, which was discovered in 1982 by two scientists Robert Gallo and Luc Montagnier, individually. This virus was found in some gay individuals who suffered from the then-unknown infection. HIV virus is believed to have come from chimpanzees. There are two types of HIV virus, simply called HIV type I and HIV type II. Type I is the most common.

HIV-1 is more dangerous and more infective and is the cause of the majority of HIV infections globally. HIV-2 is known to infect about 5% of all HIV infections., is more common in West African countries.

HIV virus infection is always routed through blood, semen, vaginal fluid, pre-ejaculation fluid (pre-cum), or breast milk. The transfer of the virus may take place through these fluids. It may transfer via genital, anal, or anal routes through sexual contact. HIV is never transmitted by air or touch.