Aids is a pandemic. According to the World Health Organization and Unaids, the Joint United Nations Programme on HIV/Aids, some 40 million people are living with HIV around the world. And more than 25 million people are estimated to have died since 1981 as a result of Aids-related diseases. In 2005, around 2.8 million people died of Aids-related illnesses, 570,000 of them children. Meanwhile, approximately 4.1 million people were newly infected.

Sub-Saharan Africa is easily the worst affected region, with between 21 million and 28 million people suffering, 64 per cent of the world's total. But numbers in eastern Europe and Asia continue to rise. Ukraine and Russia are particularly badly hit. And India has overtaken South Africa as the country with the highest number of sufferers within its borders. In the UK, US and western Europe levels of infection have stabilized, but are showing disturbing signs of a resurgence in the gay community.

The virus is passed through blood, semen, vaginal fluids and breast milk. Unprotected sexual intercourse with an infected person is the most common method of transmission. It can also be spread by contact with infected blood. HIV can cross from mother to child during pregnancy, childbirth or breastfeeding. Another common route is the sharing of needles. A person cannot catch HIV from toilet seats, or by touching, hugging or shaking hands with an affected person.

No. Scientists are working to find a vaccine, though 25 years of research has yet to yield any significant breakthrough. But HIV need not be an imminent death sentence anymore. There have been major advances in HIV treatment development. In 1996, highly active antiretroviral therapy (Haart), a daily cocktail of drugs, was introduced. This stabilizes a patient's symptoms. The result is that many people, although by no means all, can now live with HIV for decades. Despite unpleasant side-effects such as nausea and diarrhea, many of those taking these drugs have experienced a vast improvement in their general health and quality of life.

Using a clean needle for the injection of drugs and using condoms in sexual intercourse. Resistance, or ignorance, with regard to the second has been the most significant contributor to the rapid spread of HIV around the world. The Catholic Church has come in for a good deal of criticism for its opposition to the use of condoms on religious grounds.