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In 1981 a new disease was described in the USA: AIDS (Acquired ImmunoDeficiency Syndrome). Previously healthy male homosexuals became critically ill. They got diarrhoea, became emaciated and languished. Their lungs became infected with fungi that healthy people quickly overcome. Some of them also got Kaposi's sarcoma. In 1983 the causative retrovirus, HIV-1 (human immunodeficiency virus 1), was discovered by a Frenchman Luc Montagnier. This was subsequently confirmed by the American investigator Robert Gallo. A blood test for detecting the virus was put on the market in 1985. A second, related virus, HIV-2, was discovered somewhat later. This latter virus also causes AIDS and occurs more in West Africa. Infections with HIV-2 develop into AIDS more slowly than infections with HIV-1
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A whole series of HIV subtypes has been identified. HIV-1 is at present subdivided into 3 genetically different groups, each of which can be further divided into various subtypes that more or less have their own geographical distribution. The principal group is the M- ("major") group with subtypes a, b, c, d, e, f, g and h. The second group, the O- ("outlier") group, occurs principally in Cameroon. A variant (YBF 30), which represents a new group (N-group) that is more closely related to SIV (simian immunodeficiency virus) was discovered in Cameroon in 1998. This last HIV-variant was still not being detected even in 1999 by the standard AIDS tests used in hospitals. In 1998 fragments of the HIV-1 genome were discovered in an old (1959) plasma sample taken from a man from what was then Leopoldville (now Kinshasa). Data from similar old samples are important for a better understanding of the evolution of the virus and possibly for discovering the ancestral virus. The diversification of all M types appears to have taken place in less than 50 years. A closely related virus, SIV, occurs in chimpanzees. HIV-1 probably originates from SIV that occurs in a certain subspecies of chimpanzees (Pan troglodytes troglodytes). Interspecies transfer of these viruses probably occurred historically on at least 3 different occasions. Apes and monkeys are hunted and eaten in many countries and there is a strong possibility of humans coming into contact with simian blood. HIV-2 is closely related to a virus that is found in another simian species (Cercocebus torquatus atys or "sooty mangabey"). Another retrovirus, HTLV-1, possibly has its origin in mandrills (Mandrillus sp.). HIV-2 is closely related to the sooty mangabey SIV (SIVsm) and its genetic material has 40-60% homology with HIV-1.
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In all known instances of infection of the natural primate host of SIV, neither a disease resembling AIDS nor a profound depletion of CD4 T-cells develops, despite the presence of very high viral loads in these animals. In contrast, transmission of SIV to unnatural hosts, such as rhesus monkeys (Macacca mulatta), causes progressive loss of CD4 T-cells and a high degree of susceptibility to opportunistic infections.
The very high case-fatality rate, the impact on health and society and the absence of any curative treatment or vaccine, make the HIV epidemic one of the biggest health problems at the end of the 20th Century and the beginning of the 21st. The chronic nature of the epidemic and the multiple accompanying life-threatening diseases result in enormous financial costs for patients and society. The patients occupy a large number of hospital beds for a long time and often require expensive palliative care, making heavy demands on already small health budgets. This money could otherwise have been used for the prevention or treatment of curable diseases. The emphasis will come to lie increasingly on home care insofar as possible. AIDS is a very complex problem of enormous dimensions. In addition to the purely medical aspect of the disease itself, there are the equally important social aspects of discrimination, ostracism, risk of transmission, orphaned children and financial problems, as well as burdensome psychological problems such as anxiety, feelings of guilt, anger and revenge, depression and attempted suicide.
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As is the case with other infectious organisms, transmission of an organism need not automatically result in an epidemic. An occasional infection with HIV somewhere in an African village may well have been followed by infection of the sexual partner(s), resulting in their death, but without further transmission. However, ideal conditions for an epidemic were created when the demographic and social conditions were altered (mass migration from rural to urban areas, migration for work, break-up of the traditional family, increased sexual promiscuity and prostitution, including the homosexual revolution in the West and contamination of blood reserves). An explosive increase in the number of cases in homosexual men, in intravenous drug users and in haemophiliac patients was initially seen in the USA and Europe. Heterosexual transmission later became increasingly significant in the West. The virus has spread into the general population. Heterosexual transmission was at first the principal route of transmission in Africa. It is an epidemic fundamentally determined by human behaviour. In Europe, before treatment with antiviral cocktails became available, the average time elapsing between infection and the appearance of AIDS in a patient was 10 years. After 10 years 50% of the infected individuals had developed AIDS. In Europe the case-fatality rate of AIDS was approximately 100% within 4 to 5 years following the diagnosis of AIDS (data from before the era of antiviral agents). In developing countries the progression of the disease is comparable with that in Europe, though patients in these countries will die more quickly after the appearance of symptoms than those in Europe due to the lack of treatment. In addition to the enormous human toll the epidemic also takes an economic toll in terms of the direct cost of medical care, the loss of productive working years from the patient and the costs of prevention.
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Due to the success of the combined therapies the number of AIDS-related deaths in the USA fell by 44% between 1996 and 1997. At the same time the problem continued to spread unabatedly in Third World countries. If nothing fundamentally changes, the life expectancy in a number of countries will decrease further. Hence by 2010 the average lifespan in Zambia is expected to decrease from 66 to 33 years, in Zimbabwe from 70 to 40 years, in Kenya from 68 to 40 years and in Uganda from 59 to 31 years
(extrapolation if HAART would not become available in the tropics). In mid-1999 AIDS was already the fourth most important cause of death in the world, after ischaemic heart disease, cerebrovascular diseases and lower airway infections. In Africa it is the principal cause of death. In this respect the disease has overtaken malaria and tuberculosis. The epidemic results in more or less selective infection of the 15 to 45-year-old population group (reproductive years) and young children. The problem of abandoned orphans has assumed dramatic proportions in certain areas. The total number of AIDS orphans in the world at the end of 1999 was estimated to be 13,200,000. The 30% decrease in mortality expected from the institution of the EPI Programme (a World Health Organization vaccination programme) will be annulled by the increase in neonatal AIDS. In some countries such as Zambia, Zimbabwe and Botswana the classic form of the population pyramid has been altered drastically.
In the year 2000 AIDS was reported in practically every country. Approximately two thirds of all cases occurred in sub-Saharan Africa. In 2001 the cumulative mortality resulting from AIDS was estimated to be 21,800,000. About 40,000,000 persons living in 2002 are infected. These figures may be understood better by noting that approximately 14,500 new infections occur each day. In Africa the ratio of infected men / women = 1. Over the whole world somewhat more men than women are infected. Approximately 10% of the total number of seropositive persons are children under 15 years of age. The estimated numbers of persons living with HIV infection in January 2003 and the anticipated number of new infections through the year are:
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Geographical Area |
People 0-45 years old, living with HIV/AIDS, December 2003 |
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North America |
790.000 - 1.2 million |
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Caribbean |
350.000 - 590.000 |
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Latin America |
1.3 - 1.9 million |
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Western Europe |
520.000 - 680.000 |
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Eastern Europe - Soviet Union |
1.2 - 1.8 million |
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Sub-Saharan Africa |
25.0 - 28.2 million |
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Middle East + North Africa |
470.000 - 730.000 |
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India and Southeast Asia |
4.6 - 8.2 million |
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Far East |
700.000 - 1.3 million |
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Australasia |
12.000 - 18.000 |
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Total |
34 - 46 million |
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Global summary of the HIV/AIDS epidemic, December 2003 (UNAIDS data)
Number of people living with HIV/AIDS
Total: 40 million (34-46 million)
Adults: 37 million (31-43 million)
Children under 15 years: 2.5 million (2.1 - 2.9 million)
People newly infected with HIV in 2003
Total: 5 million (4.2 - 5.8 million)
Adults: 4.2 million (3.6 - 4.8 million)
Children under 15 years: 700.000 (590.000 - 810.000)
AIDS deaths in 2003
Adults: 2.5 million (2.1 - 2.9 million)
Children under 15 years: 500.000 (420.000 - 580.000)
