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HIV

Infectious agent identified as the cause of AIDS. It was first discovered in 1983 by Luc Montagnier of the Pasteur Institute in Paris, who called it lymphocyte-associated virus (LAV). Independently, US scientist Robert Gallo of the National Cancer Institute in Bethesda, Maryland, claimed its discovery in 1984 and named it human T-lymphocytotrophic virus 3 (HTLV-III).

Transmission

Worldwide, heterosexual activity accounts for three-quarters of all HIV infections. In Europe and the USA, high-risk groups are homosexual and bisexual men, prostitutes, intravenous drug users sharing needles, and haemophiliacs and other patients treated with contaminated blood products. The different distribution of risk in developed and developing countries occurs because different types of the virus are more common in different regions. The virus has a short life outside the body, which makes transmission of the infection by methods other than sexual contact, blood transfusion, and shared syringes extremely unlikely. Pregnant women infected with HIV are unlikely to pass it on to the fetus while in the uterus, but are quite likely to do so via vaginal fluids during birth or after breast-feeding the child. More than 90% of children born to an HIV-positive mother will contract the disease unless their parent has been treated with antiretroviral drugs.

To prevent the spread of HIV, evidence indicates a need to take early action and to invest in publicity and education campaigns. The second key element is to test pregnant women for HIV and give them antiviral drugs if they are HIV-positive, to prevent the transmission of the virus to the baby during childbirth.

A study published in May 2001 by the Center for Disease Control and Prevention (CDC) found that while the average annual incidence for HIV among all US gay and bisexual men is about 4%, 15% of gay and bisexual black men between the ages of 23 and 29 become infected with HIV – four times the rate among Hispanics and five times that of whites. In December 2002, the CDC published a report breaking down the HIV/AIDS statistics into ethnic groups. They found that found that of the 384,906 people infected with HIV, 46% were white, 34% were black, and 18% were Hispanic. Less than 2% belonged to the Asian and Pacific Islander communities and less than 1% was found in American Indian and Alaskan Native populations. During 2002 35,247 new cases of HIV infection were diagnosed in the USA.

The development of HIV Many people who have HIV in their blood are not ill; in fact, it was initially thought that during the delay between infection with HIV and the development of AIDS the virus lay dormant. However, US researchers estimated in 1995 that HIV reproduces at a rate of a billion viruses a day, even in individuals with no symptoms, but is held at bay by the immune system producing enough white blood cells (CD4 cells) to destroy them. Gradually, the virus mutates so much that the immune system is unable to continue to counteract; people with advanced AIDS have virtually no CD4 cells remaining. These results indicate the importance of treating HIV-positive individuals before symptoms develop, rather than delaying treatment until the onset of AIDS.

HIV statistics By the end of 2003, the report of the joint United Nations programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimated that worldwide there were 37 million HIV-positive adults and 2.5 million children, of whom 95% lived in the developing world. In sub-Saharan Africa, HIV infections numbered 26.6 million, in Asia and the Pacific 7.4 million, in Latin America and the Caribbean 2 million, and in North Africa and the Middle East 600,000.

In 2002 there were 384,906 people living with HIV in the USA and 49,500 in the UK.

In 2003 there were 5 million new cases of HIV infection worldwide – around 14,000 new cases a day. Despite antiretroviral drug treatments, 3 million people died of HIV/AIDS-related deaths in 2003.

HIV and babies In 1997, around 1,000 babies infected with HIV were born every day. It is believed that more than 5 million children have been infected this way, of whom 4 million have already died. However, the rate of HIV-positive babies born with HIV was falling in the USA (fewer than 500 a year) and in Europe, as a result of HIV testing and the use of antiviral drugs during pregnancy. In the UK in 1998, the percentage of HIV babies born to HIV-positive mothers was 2.2%, compared with 17.6% in 1993. The fall is due to the use of antiviral drugs in late pregnancy, voluntary HIV testing, counselling, delivery by Caesarean section, and bottle-feeding infants. These precautions are more difficult to provide in developing countries, and consequently the incidence of HIV-positive births is higher in these areas. Until recently, AZT, or zidovudine, has been the main antiviral drug used to prevent transmission of the disease during birth. It has been too expensive for widespread use in Africa, but recent studies in Kenya and South Africa have shown that another cheaper drug, nevirapine, is also effective. Bottle-feeding formula milk is also expensive and has health risks for the baby, such as disease caused by unclean water. Between 1991 and 2002 there was an 80% decrease in the number of babies born with HIV in the USA.

HIV variants and risk US researchers in 1995 developed an explanation of why HIV is transmitted mainly by heterosexual sex in Africa and Asia, and by homosexual sex and intravenous drug use in Europe and the USA. They found that the HIV variant subtype B – responsible for 90% of European and US cases – did not grow well in reproductive tract cells, whereas subtype E – common in developing countries – did grow well. If subtype E becomes more prevalent in Europe and the USA, infection patterns will probably change. The first case of subtype E in Britain was documented in May 1996. A new strain of HIV was discovered in Cameroon in 1998 by French researchers. However, this particular strain is very rare and has been detected in only three other people, all of whom were also from Cameroon.

Intercourse between high- and low-risk groups is known as disassortative mating. The areas of the world with the highest rates of HIV incidence, sub-Saharan Africa and the Caribbean, have particularly high levels of disassortative mating between older men (with a higher likelihood of having picked up the virus than younger ones) and young women. Epidemiologists have demonstrated that to stop an epidemic growing, it is essential to ensure that the average number of people infected by someone who already has the virus is kept to below one.

Prevention programmes Senegal and Uganda are two African states that have had significant success in halting the spread of HIV. Senegal began its anti-HIV/AIDS campaign in 1986 when incidence was still low, and has managed to keep the infection rate at below 2%. Uganda began its programme in the early 1990s and had brought down the infection rate from 14% of the adult population to 8% by 1999. The key elements of the programmes have been the widespread promotion of condoms to reduce the rate of transmission between adults and, overcoming the taboo on talking about sex, educating girls and young women on the importance of condom use. In Senegal, the number of condoms used annually increased more than tenfold between 1988 and 1997 to 9 million.

Research published in July 2000 in the UK medical journal Lancet advocated offering free sex counselling and HIV tests to people in the developing world to curtail unsafe sex as a means of decreasing infection rates by more than 10% each year. A UN- and US- commissioned study in Kenya found that 1,104 HIV infections were averted for every 10,000 tests carried out.

In February 2003, the results of a five-year study of prevention programmes in Ethiopia showed that annual infection rates had decreased from 1.2% to 0.4% over the length of the study. Voluntary counselling and testing programmes and increased use of condoms were cited as being responsible for the effectiveness of the prevention programmes. In 2003, HIV/AIDS education programmes in factories in Zimbabwe reduced the number of new infections by 34% compared with workplaces that had received no prevention programmes. However in South Africa, in 2003, less that 20% of those at risk of HIV infection had access to prevention measures.

The Global HIV Working Group estimated worldwide spending in 2002 for HIV prevention to be $1.9 billion. This figure is far short of the $6 billion that UNAIDS estimates is required annually by 2005 to contain the spread of the disease.

Vaccines In 1991, the World Health Organization (WHO) spearheaded a vaccine development effort centred on Brazil, Thailand, and Uganda. With the creation of UNAIDS in 1996, the programme was taken over by the UN organization. Trials of an HIV vaccine began in the USA in June 1998 with 5,000 high-risk volunteers (gay men and those with HIV-infected partners) receiving the vaccine or a placebo. Significant results will take several years to become apparent. An HIV vaccine trial began in Uganda in February 1999, the first African trial of an HIV vaccine (the vaccine has already been tested on French and US volunteers). HIV-negative volunteers were vaccinated with a weakened canarypox virus carrying three HIV genes. In February 2000, WHO and UNAIDS joined together to launch a new initiative to foster international cooperation in the development of a vaccine that would be effective in both the developed and the developing world.

In February 2003, US biotechnology company VaxGen announced that their 3-year study of a vaccine on a group of 5,000 volunteers had resulted in only a limited success. Overall, their vaccine was only able to reduce the rate of HIV infection by 3.8%. However there was some hope of a partial use for the drug, as it was able to reduce the infection rate among black and Asian volunteers by 67%. VaxGen tested their vaccine AIDVAX in Thailand in November 2003, a programme involving 2,500 drug users, but this trial was a failure with the vaccine being unable to prevent the spread or progress of the disease.

A substantially effective vaccine would have a major impact on halting the spread of HIV if it could be supplied at a price to make it feasible for use throughout Africa and Asia. A charity based in New York City, the International Aids Vaccine Initiative (IAVI), has supplied investment support to a number of vaccine development initiatives on the understanding that an eventual product would be sold at a low profit margin.

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