Over 40 million people worldwide are infected with the HIV virus and infection rates in women are increasing.

In the 20 years since HIV, or human immunodeficiency virus, was discovered, more than 60 million people have been infected. At first thought of as a 'gay' disease, HIV is no respecter of age or sex and is the most devastating disease the human race has faced. It's the virus that eventually causes acquired immunodeficiency syndrome or Aids - a disease that attacks the immune system and leaves the body vulnerable to serious illnesses.

HIV is different from other viruses because antibodies produced by the immune system cannot kill HIV. Once a person is infected, HIV remains in the blood forever. Since 1992 about half the people with HIV have developed Aids within 10 years of initial infection.

The time between HIV infection and the development of Aids varies greatly - it depends on many factors, including a person's general health and his or her health-related behaviour. With improved treatment, researchers anticipate that the time it takes to develop full-blown Aids will extend further.

Who is affected?
In the UK, over 31,000 people including 500 children had either Aids or HIV at the beginning of 2,000 and 450 people died of Aids in the same year. For the past decade, HIV infections among UK women have increased dramatically, as have other - curable - sexually transmitted infections. In 1992, women made up 12 per cent of people living with Aids. By 1998, the proportion had grown to 35 per cent. Today, around 9,000 women in the UK are living with HIV infection, including those with Aids.

Worldwide, about 14 million women of childbearing age are infected with HIV, and more than 90 per cent of these are as a result of heterosexual transmission.

Thanks to powerful new antiretroviral drugs, the number of AIDS cases in both men and women in the UK has declined steadily. Recently, the decline in Aids has levelled off, indicating that much of the benefit of new drugs has been realised. But at the same time, complacency toward safe sex from over-optimism about HIV treatment has worried health officials. New studies have identified disturbing increases in HIV infection among young gay men and high-risk adolescents. This letting down of the prevention guard has already led to an upswing in HIV cases in the year 2000.

How is the infection passed on?
HIV is transmitted through the blood, semen and vaginal secretions of an infected person. Transmission occurs through:

• Unprotected sex, and sharing needles with an HIV-infected person
• Childbirth - babies born to HIV-infected women may become infected before or during birth, or shortly after birth through breast-feeding
• Household settings - although rare, a few cases of HIV have been transmitted in household settings when infected blood or other body fluids came in contact with skin or mucous membranes

• Experts recommend against 'French' or open-mouthed kissing with an infected person because of the possibility of contact with blood (casual contact through closed-mouth or social kissing is not a risk factor for transmission of HIV)
• The risk of acquiring HIV from an infected health care worker is extremely low, and only two cases worldwide have been documented of an HIV-positive surgeon transmitting the virus to a patient
• Female-to-female transmission of HIV appears to be low, but case reports of female-to-female transmission indicate that vaginal secretions and menstrual blood are potentially infectious and that mucous membrane (e.g. oral and vaginal) exposure to these secretions has the potential to lead to HIV infection

Six months onwards. In the next stage, the symptoms usually go away while the body continues to defend itself by producing antibodies, but the virus continues to multiply and infect immune cells. This stage may last for many years.

Development of Aids
Later, as the disease progresses, more serious symptoms emerge such as weight loss, prolonged fever and diarrhoea. The damage to the immune system allows other infections to occur, which include shingles, pneumocystis pneumonia (PCP), tuberculosis, cytomegalovirus and fungal infections. Unusual cancers such as Kaposi's sarcoma may also occur.

How is it diagnosed?
As HIV infection may give no symptoms at all for a long time, diagnosis is based upon a blood test that detects antibodies to the virus. This test can be done by your GP or at a hospital department of genito-urinary medicine (also known as a GUM clinic), where you can attend without an appointment. It is important you receive counselling before the test to help you decide whether to have it, and how to cope with the results afterwards.

What do HIV tests include?

• An initial screening test - this picks up nearly all cases of HIV infection but occasionally gives a 'false positive' answer
• Second, confirmatory, tests if the first is positive - at least two further tests are done on the blood sample to make sure that no one is told they are HIV positive in error

This more specific second test can differentiate between HIV antibodies and other antibodies that react to the EIA, causing positive results even when the person is not actually infected with HIV. Although false-positive EIA results are uncommon, they can occur when the test mistakes other antibodies that the body has made for HIV antibodies.

What if the test is negative?
If your HIV antibody test is negative, you are either uninfected or in the early stages of the production of HIV antibodies.

This early period before development of HIV antibodies, which would not be detectable on a test, is called the seroconversion time or period. Some have referred to this time as the 'window period,' since this is the window of opportunity for persons to unknowingly infect others. The average time for detectable HIV antibodies to develop is 25 days. In some cases a test result is indeterminate or equivocal, meaning it is too early for detection of HIV antibodies or your blood has produced something to cause a test reaction. If an indeterminate reading continues for six months or longer, you are considered uninfected.

How is HIV treated?
Treating HIV is one of most rapidly evolving fields in medicine. New therapies, different combinations of drugs and improved methods for monitoring infection make treatment increasingly complex. If you are HIV positive you will be put under the care of a specialist in HIV medicine who will know what the current treatment should be.

There are three important facts about treatment for HIV:

• It is available - and valuable - for HIV-infected persons who are asymptomatic, without symptoms
• It can prevent several illnesses that come with late-stage HIV infection
• HIV therapy and drug development change all the time, so it's important to keep up with latest findings

• Treatment should start early. Researchers now know that drug therapy initiated soon after infection can dampen the initial viral surge that spreads through the body. By keeping the virus in check, the drugs can delay the gradual weakening of the immune system.
• Treatment helps stop spread. Effective treatment is likely to reduce the chances of an infected person transmitting the virus: drugs not only lower the amount of virus in the blood but in bodily fluids as well.
• Treatment delays illness. People on early treatment with powerful drug combinations can delay symptoms of infection longer - and possibly indefinitely - than those not on treatment.

You have probably heard how these miracle drugs used in different combinations have allowed patients once disabled by Aids to return to work and remain free from serious symptoms. However, the long-term impact of these drugs remains unknown. Once the drugs are stopped, the virus often returns in full force. Moreover, there are HIV strains developing that can resist the drugs.

Despite these factors, the consensus is that treatment should be early and aggressive. And while this means taking up to 20 pills a day (or more) and facing significant side effects, HIV has become a condition that can be managed, much like diabetes or high blood pressure.

During your treatment, tests will be carried out to monitor the course of the infection. Two such tests monitor the 'viral load' - the amount of virus present - and the level of 'CD4' immune cells in the blood.

Types of drugs used to treat HIV
Drugs currently in use fall into three groups:

• Nucleoside reverse transcriptase inhibitors, such as AZT that target an enzyme HIV uses known as reverse transcriptase
• Non-nucleoside reverse transcriptase inhibitors, such as delavirdine, which also target the enzyme but work differently way
• Protease inhibitors, such as indinavir, which prevent HIV from making copies after it has entered a cell

More common side effects from antiviral drugs are headache, fever rash and nausea. Because HIV treatment requires combinations of two or more drugs, the risk of adverse interaction is greater than treatment for most other conditions. This is one more reason you should receive treatment from a doctor experienced in HIV care.

How can it be prevented?
Since the beginning of the epidemic, prevention measures for HIV have remained unchanged. As research uncovers more about genetic differences that seem to account for why some HIV-positive persons never develop symptoms, new avenues will open up for vaccine development. Work is also progressing on development of a microbicide that can protect women from HIV, possibly without killing sperm. Despite this, a preventive measure women can control is years away.

The means of preventing HIV are simple. It's the behaviour change that is so hard - and so critical. To prevent HIV infection, you have to avoid behaviour that might result in contact with blood, semen, vaginal secretions or body fluids with visible blood. Specifically, avoid sex with anyone who might be infected with HIV, and do not share 'drug injection supplies.'

You can take the following prevention measures to avoid getting the virus:

• Abstain from sex with an infected person
• Ask about the sexual history of current and future sexual partners
• Reduce the number of sex partners
• Always use a condom from start to finish during any type of sex - vaginal, anal and oral - and use latex condoms rather than natural membrane condoms as they offer good protection against sexually transmitted infections, including HIV
• Use water-based lubricants, not oil-based lubricants such as petroleum jelly - if you decide to use a spermicide along with a condom, make sure you use it according to the manufacturer's instructions
• Avoid anal or rough vaginal intercourse - do not do anything that could tear the skin or moist lining of the genitals, anus or mouth
• Condoms should be used even for oral sex - studies have found that even with repeated sexual contact, 98-100 per cent of those people who use latex condoms correctly and consistently do not become infected
• Avoid deep, wet or 'French' kissing with an infected person, as possible trauma to the mouth may occur, which could result in the exchange of blood (it is safe, however, to hug, cuddle or dry kiss your partner)
• Avoid alcohol and illicit drugs, as they can impair your immune system and your judgement - if you use drugs, do not share needles or syringes
• Do not share personal items such as toothbrushes, razors and devices used during sex that may be contaminated with blood, semen or vaginal fluids

• Exposure of a mucous membrane, such as the mouth (especially non-intact tissue) to vaginal secretions and menstrual blood is potentially infectious, particularly during early- and late-stage HIV infection when the amount of virus in the blood is expected to be highest
• Condoms should be used consistently and correctly each and every time for sexual contact with men or when using sex toys with men or women, and sex toys should not be shared
• No barrier methods for use during oral sex have been evaluated as effective, but women can use dental dams, cut-open condoms or plastic wrap to help protect themselves from contact with body fluids during oral sex

For those who are already infected, combinations of new antiviral drugs may decrease the ability to transmit the virus to a partner. The concept is only theoretical at this time but research has shown, for example, that the drugs reduce the amount of virus in semen and vaginal secretions. Until the impact of treatment on transmission has been determined by large studies, this should not be considered a form of prevention.

Mother and baby risk
HIV infection can be passed from mother to baby before or during birth and through breastfeeding. Among HIV-infected pregnant women who have not received any preventive treatment, mother-to-infant HIV transmission rates range from 15-25 per cent in developed countries, to 25-45 per cent in developing countries where an estimated 1,800 HIV-infected babies are born each day.

Research has demonstrated that drugs can prevent mother-to-infant transmission. When women and their infants receive the antiretroviral drug, AZT, the risk of transmission is lowered nearly three fold. Any pregnant women in the UK may have an HIV test if she wishes, but these tests are not routine.

HIV-infected women are more likely to experience gynaecological disorders than HIV-negative women, and are much more likely to have abnormal cervical smears. Consequently, screening more frequently is advised for women with symptomatic HIV infection, prior abnormal cervical smears or signs of human papillomavirus infection (HPV), a sexually transmitted disease that causes genital warts and lesions.