HIV (Human Immunodeficiency Virus) is the virus that causes the disease AIDS (Acquired Immunodeficiency Syndrome). AIDS is the group of illnesses acquired when the body's immune system breaks down and is unable to fight off infections, known as "opportunistic infections," and other illnesses that take advantage of a weakened immune system.

India has the third largest number of people in the world living with HIV/AIDS. However, there has been a 50% decline in the number of new HIV infections in the last 10 years in India. There is no cure or effective vaccine for HIV at this time. Anti-retroviral therapy is used to slow progression of the disease and prevent opportunistic infections.