AIDS (acquired immune deficiency syndrome) was first recognised in 1981 in the US, when doctors found that large numbers of homosexuals were dying from causes that were almost unidentifiable. It was in 1983 scientists discovered a viral infection was attacking the immune system which guards the body against disease.

AIDS became a pandemic. In 2014, it was estimated 40 million people around the world had died as a result of AIDS. In the UK, there is an estimated 100,000 living with the disease. Experts think it originated among primates in central Africa and spread to humans at the turn of the twentieth century. People do not die from AIDS, rather from simple infections that their weakened immune system cannot fight off. AIDS is usually caused by the following:

Unprotected sex with someone who has AIDS
Sharing hypodermic needles
Contaminated blood transfusions
From a mother to a child during pregnancy or breast-feeding