HIV stands for human immunodeficiency virus and on its own it does not kill you.
The virus can survive and grow only by infecting, and destroying, the immune system.
This continual assault on the immune system makes it weaker and weaker until it is no longer able to fight off infections.
Without treatment, it takes about 10 years from infection to the development of Aids - acquired immune deficiency syndrome.
It is then that "opportunistic infections", which a healthy immune system could fight off, become deadly.
People can die from pneumonias, brain infections, diarrhoeal illnesses as well as certain tumours such as lymphoma and cervical cancer.