What are the symptoms?

Aids stands for acquired immune deficiency syndrome. People with HIV (human immunodeficiency virus) can look and feel well.

As the virus attacks the immune system, an infected person will be open to a large number of illnesses. This means there are a wide variety of symptoms.

HIV usually leads to Aids, which is diagnosed when a person has developed one of several opportunistic diseases associated with the virus as well as underlying immune problems.

The diseases include pneumonia, Kaposi's sarcoma - a form of purplish skin cancer not normally seen in young people before the advent of Aids - and dementia.

How is it transmitted?

HIV is relatively difficult to transmit as it does not live for long outside the body.

It is carried in the semen, vaginal fluids, breast milk and blood.

The main transmission routes are through sharing needles, sex, blood transfusions, transplants, getting infected fluid into open wounds and breast feeding.

High risk groups or behaviour

Certain groups are believed to be at higher risk of developing the virus. These include those who share needles and children who are breast fed with infected milk. As the disease began in the West in the gay community, gay men are at higher risk than heterosexuals. Sex workers and those who have multiple sexual partners are also at higher risk than average. People with other sexually transmitted diseases are also thought to be more likely to contract HIV than others.

What is the treatment?

If you want to know if you have HIV, you should contact your doctor or a sexually transmitted disease clinic about a blood test. They will usually suggest counselling before you take an HIV test to make sure you are prepared for all the implications of the result, including the impact on life insurance and mortgages. Aids organisations have reported that, in some cases, just taking the test can be enough for some companies to refuse you insurance or a mortgage.

If you test positive for the virus, there are a range of treatments you may be offered. The most popular is combination therapy, a cocktail of different anti-Aids drug, including AZT. The drugs can have powerful side effects, such as anaemia, and not everyone responds well to them.

People who take the numerous drugs have to stick to a rigid regime, but they have been shown to reduce the virus and rebuild the immune system. In some cases, the virus has been reduced to undetectable levels. However, doctors say it is too early to say yet how long they will last.

Stigma

Because of the way HIV is transmitted and the groups it has affected most - including drug users, gay men and people immigrant communities, it has attracted much media attention and prejudice. This has often made it hard for sufferers to come forward for testing. The all-parliamentary group on Aids says tackling the stigma of the disease is vital for reducing its impact.

Reducing the risk

The main advice from health promotion units includes using a condom for sexual intercourse. Injecting drug users are advised not to share needles. In many areas of the UK, health officials operate a needle exchange scheme where clean needles can be obtained free of charge.

UK statistics

Sixty-three per cent of the 32,242 cases of HIV in the UK (as of July 1998) are thought to have been acquired through gay sex and 21% through heterosexual sex.

The number of heterosexual cases has risen from 9% in 1987 to 31% in 1997. Three quarters of these cases were probably acquired abroad, the vast majority in Africa. HIV is at epidemic proportions in southern, western and central Africa. In Zimbabwe, the projected number of cases is likely to almost half the life expectancy rate in the next 25 years. The number of cases in south east Asia is also set to soar over the next few years.

However, in general, the risk of spread by heterosexuals who are bisexuals, injecting drug users and haemophiliacs has not been as great as was feared in the early days of the disease. Only 8% of cases of UK transmission are thought to have been infected by people in this category. Experts say this could be due to the UK's relatively low level of IV drug infection and the role of sexually transmitted disease (STD) clinics in reducing the spread of infection. However, experts say a recent rise in STDs is cause for concern and add that Aids awareness campaigns should not be relaxed.

Where in the UK are heterosexual cases concentrated?

Distribution of cases is uneven. Many are in Scotland, due to a wave of IV drug infection in the early 1980s. The London area, where there is a high concentration of immigrants from Africa, also has high figures.Women account for 55% of cases, but experts say this could be because they are more likely to be diagnosed, for example, if they get pregnant.

Many, however, do not know they are infected. Anonymous surveys show that many as 50% of heterosexuals attending STD clinics in London do not know they are infected. Anonymous surveys at ante-natal clinics show that up to 78% of women in England and Wales have not been officially diagnosed as having HIV.

Where to go for help

Expert advice is available from the The Terrence Higgins Trust, 52-54, Gray's Inn Road, London WC1X 8JU. Helpline: 0171-242 1010.