mother to child.4 Mortality from HIV-2 may have been only about one-third of that from HIV-1, for viral loads were generally lower, those infected were often older, and progression to Aids might take on average as much as 25 years, so that many of those infected never reached that stage, although if they did the final illness was similar.5 Given that the opportunistic infections fatal to Aids patients were often those common to the local disease environment, it was understandable that HIV-2 passed unnoticed until 1985, when researchers investigating the existence of HIV-1 in Senegal discovered the other virus almost by chance.6 This probably explains why HIV-1 and HIV-2 appear to have emerged virtually simultaneously: the appearance is an optical illusion.
Once the discovery was made, retrospective testing of the earliest stored blood for HIV-2 antibodies revealed an intriguing pattern.7 Apart from one obscure reference to an alleged case in Mali in 1957, the earliest may have been a Portuguese man who had lived in Guinea-Bissau between 1956 and 1966. Other infections there during the 1960s are also recorded. Five cases were found in Côte d’Ivoire during the 1960s. Stored blood taken in 1967 also revealed two cases each in Nigeria and Gabon, both outside the range of sooty mangabeys and presumably infected through travel. They were followed in the 1970s by infections from Mali, Senegal, and Angola, the last probably transmitted through the movement of Portuguese troops from Guinea-Bissau. By the 1980s scattered cases were reported from many parts of western Africa, often from the countryside, suggesting a low-intensity disease much like HIV-1 in its pre-epidemic days in western equatorial Africa. In Guinea-Bissau, however, the liberation war of 1960–74, the presence of Portuguese troops, the movement of refugees, and perhaps especially the widespread use of injections by Portuguese military doctors appear to have bred a localised and probably unique epidemic.8 Hospitals in Portugal later treated many cases contracted in Guinea-Bissau at this time. A study in Bissau town in the late 1990s showed that levels of infection peaked among men in their sixties and women in their fifties who would have been sexually most active during the 1960s. Prevalence there among men who had served in the Portuguese army was 23 per cent; among the nineteen women who had had sex with white men it was 37 per cent. This wartime legacy gave Guinea-Bissau much the highest prevalence of HIV-2. In the mid 1980s, 26 per cent of paid blood donors there tested positive, as did 8.6 per cent of Bissau’s pregnant women and 36.7 per cent of its sex workers in 1987.9 Ten years later HIV-2 infected 13.5 per cent of people over 35 living on the outskirts of the town. High levels were also reported in rural areas and spilled over (largely through migrant sex workers) to southern Senegal and The Gambia.10 Yet the epidemic never spread beyond this region. That would presumably have required a virus more infectious than HIV-2.
HIV-1 was such a virus. Its arrival in West Africa (as distinct from western equatorial Africa) is difficult to trace but possibly took place in about 1980, slightly after its appearance in East and Central Africa. A claim to have discovered one case in stored blood taken in Burkina in 1963 can almost certainly be dismissed. A Malian migrant who had never visited equatorial Africa died in Paris in 1983 with Aids-like symptoms, although this could as well have been HIV-2 as HIV-1. Ghanaian doctors came to believe that they had seen Aids cases as early as 1981, but no details are available and HIV-2 would again have been possible.11 Otherwise, the earliest evidence comes from Côte d’Ivoire. Retrospective tests on stored blood taken there between 1970 and 1983 all proved negative. Adult mortality in Abidjan declined until 1985, the year when its first Aids cases were diagnosed, and then began to increase rapidly. In 1985, 38 of 79 sex workers were found to be infected there, together with 10 of 71 in the northern Ivoirian town of Korhogo. A year later HIV-1 prevalence was 3.0 per cent among pregnant women and 4.9 per cent among hospital staff in Abidjan. French researchers concluded that the first HIV infections there probably took place in about 1980.12 Observers suggested at the time that the city’s sex workers might have been infected by European tourists, but this is unlikely because the B subtype of HIV-1 prevalent in Europe did not become established in Abidjan or elsewhere in West Africa. Rather, the dominant strain came to be CRF02_AG, the circulating recombinant form rare in the DR Congo but common in Cameroun and Gabon, implying a northward diffusion comparable to the eastward diffusion of subtypes A and D into East Africa – a diffusion that in West Africa could have been carried in the first instance along the coast by sex workers and their clients moving between Libreville, Douala, and Abidjan. CRF02_AG became dominant among West Africa’s coastal sex workers, throughout Côte d’Ivoire (where in the late 1990s it was responsible for over 90 per cent of HIV-1 infections), in southern Nigeria (causing 70 per cent of the entire country’s infections), and in most coastal areas as far west as Senegal.13 In some inland savanna regions, including northern Nigeria, another recombinant form, CRF06_cpx, was sometimes more common (cpx signifying a complex of more than two subtypes).14
Map 4 West Africa
There were several reasons why Abidjan and Côte d’Ivoire should have become the focus of West Africa’s HIV-1 epidemic. Neglected until late in the colonial period but endowed with vast areas of virgin tropical forest, Côte d’Ivoire experienced rapid development during the first two decades of independence, with a 6.8 per cent annual growth rate of real Gross Domestic Product between 1965 and 1980.15 Sparsely populated, its prosperity attracted immigrants both from economically faltering neighbours like Ghana and from the poorer savanna countries to the north. By the late 1980s some two million migrants from Burkina, over one million from Mali, and large numbers from Niger were present in Côte d’Ivoire at any time. Although many migrants worked in agriculture, over half lived in cities, especially in Abidjan, whose development as a major port increased its population between 1955 and 1984 from 120,000 to nearly 1,800,000. In 1975 some 40 per cent were non-Ivoirian immigrants. In older West African cities the control of retail trade by women fostered a rough equality of numbers between the sexes, but Abidjan, alone in West Africa, had the large male majority among adults that in East African cities like Nairobi led to highly commercialised sex, although in Abidjan it led also to more sophisticated forms of courtesanship, owing to the greater economic independence of women in West Africa and the region’s less constrained sexual traditions.16 Like Nairobi, Abidjan was a primate city on which the whole of Côte d’Ivoire’s excellent transport system focused. And as Vinh-Kim Nguyen has shown,17 two other features of Abidjan helped to make it an epicentre of HIV infection. One was an aspiration to modernity that bred individualistic choice, extreme differences of wealth, sexual adventurism – the median age of sexual debut was fifteen18 – and complex, disassortative networks through which HIV could pass. In 1994, 51 per cent of Abidjan’s men aged 20–24 said they had casual sex and 56 per cent never used a condom.19 The other circumstance favouring an epidemic was the economic crisis that struck Côte d’Ivoire during the 1980s as the world economy faltered and the easy growth opportunities of the 1970s were exhausted. This bred unemployment, sexual commercialisation, weakened health services, and resort to Abidjan’s 800 informal dispensaries ‘that sprout like mushrooms after rain’.20
When HIV-1 prevalence was first measured in Abidjan in 1985, the city was on the verge of an epidemic more explosive than those in Kinshasa or even New York, with an annual incidence of new infections of over 3 per cent in 1989.21 The core were the city’s sex workers and their male clients. Between 1986 and 1993 HIV prevalence among sex workers rose from 38 to 86 per cent; at the latter date 50 per cent had HIV-1, 2 per cent HIV-2, and 34 per cent both. Studies showed that contact with sex workers was the chief risk factor for men, largely explaining why in 1988 men outnumbered women by nearly five to one among HIV-positive patients admitted to city hospitals and why 83 per cent of the 24,735 people estimated to have died of Aids-related diseases in the city between 1986 and 1992 were men. Deaths were most common among informal sector workers in the older working-class quarters.22 By 1991, however, as the Minister of Health put it, the epidemic ‘is in the process of passing from populations at risk to the general population,’ as HIV-positive men infected their wives and other partners, creating a second peak of incidence. By 1993, the ratio of men to women infected had fallen to less than two to
