AIDS stands for Acquired Immune Deficiency Syndrome, and the disease is caused by the human immuno-deficiency virus, known as HIV. Once it is inside the body, this virus invades the white blood cells, which normally fight off disease, then it multiplies and destroys them. It also breeds inside the brain. Three to four years normally elapse between infection with HIV and any subsequent development of the symptoms associated with AIDS.

As AIDS develops the body's natural defences become depleted, and the AIDS patient is increasingly likely to contract diseases that a healthy body would normally ward off, and so rare forms of cancer and pneumonia develop. Sometimes AIDS patients are attacked by several infections at once, such as candida, herpes and TB. At the same time, the brain may succumb to increasingly severe dementia. Somewhere between one in ten and one in three of those infected with HIV are likely to develop AIDS. As yet there is no cure for AIDS. AIDS usually progresses through various infections and stages of increasing debility to the eventual death of the sufferer.

How to avoid AIDS:

• Always use a condom.
• Avoid anal sex.
• Don't share toothbrushes, razors or any other instrument that might transfer blood from cuts or abrasions.

The virus is present in body fluids, primarily semen and blood. It may also be present in saliva, though research indicates that saliva seems to present little risk. Having anal intercourse with an infected partner is the most likely way of catching AIDS, and 80 per cent of the cases so far have been male homosexuals.

The second most common way of contracting the disease is through infected blood. Almost a quarter of the haemophiliac population now carry HIV because they have been injected with the clotting agent collected from infected blood. (Haemophiliacs are born without the blood-clotting factor, and can suffer severe bruising from a minor injury, and bleed to death from a cut unless they receive the clotting factor from donated blood.) HIV in the blood may also be transmitted on infected needles, and drug addicts are the third most highly at risk group of the population.

To become HIV positive you do not have to be homosexual or promiscuous, a drug addict or a haemophiliac. Heterosexuals are also at risk. Even a heterosexual in a steady relationship stands the risk of contracting the disease if their partner has been infected in a previous relationship. Therefore when embarking on any new relationship, it is safest to wear a condom.