Acquired Immunodeficiency Syndrome (AIDS) is caused by a retrovirus known as the Human Immunodeficiency Virus (HIV), which infects cells of the human immune system, destroying or impairing their function.

This disease has no early symptoms but as the infection spreads, the immune system becomes weaker and weaker, and the infected person becomes more vulnerable to diseases.
The highly advanced stage of HIV infection is known as Acquired Immunodeficiency Syndrome (AIDS). It can take 10-15 years for an HIV-infected person to develop AIDS; antiretroviral drugs can slow down the process even further.

Mode of Transmission
HIV is transmitted through unprotected sexual intercourse, transfusion of contaminated blood, sharing of contaminated needles, and between a mother and her infant during pregnancy, childbirth and breastfeeding.