Further north, in Niger and Mali, these patterns were repeated but at lower levels of disease and with larger proportions of locally born sex workers. In Niger, for example, 62 per cent of the first 40 Aids cases diagnosed at Niamey hospital were former migrants to the south; their risk factors were listed as ‘prostitution, contact with prostitutes, blood transfusions and histories of visits to coastal countries’. Nearly three-quarters were men, a balance that shifted during the 1990s as infection spread more broadly, although still at relatively low levels. In 2003 adult prevalence was just over 1 per cent, but with 38 per cent among sex workers in Maradi.33 Prevalence was somewhat higher in Mali, averaging 1.7 per cent in adults aged 15–49, according to a population survey in 2001, but with 30 per cent infection among sex workers and significant concentrations in Bamako and in towns like Sikasso and Mopti on migration routes to the south. Some 63 per cent of sex workers in Mali’s four main towns at that time came from outside the country.34 Low overall prevalence characterised other Sahelian regions like Mauritania and northern Chad, where, as in Sudan, levels of infection were higher in the south.35
The pattern suggests that the savanna region’s Islamic social order may have limited the transmission of disease. In Niger, for example, a population survey in 2002 showed exceptionally low infection among young people, only about 0.3 per cent for men and 0.1 per cent for women. Women in this region married very young – a median age of sixteen in Mali – to men nine or ten years older. Often secluded, only 0.1 per cent of women in Niger reported more than one sexual partner in the last twelve months when surveyed in 1998. Most of the 11 per cent of men who reported paying for sex during that year were unmarried. Moreover, whereas women in West African coastal countries practised postpartum abstinence for 10–19 months, during which their husbands often sought other partners, in Mali and Niger the average was only 4–8 months.36 The data suggest that in this Islamic region non-marital sex was to an unusual degree confined to commercial sex workers and young, unmarried, circumcised men, where it was least likely to spread infection to the general population. The same seems generally to have been true in North Africa, where, except in Sudan, official prevalence figures at age 15–49 were generally 0.1 per cent or less and about 100,000 people were thought to be infected in 2005. Although many of the earliest cases there were introduced from Europe by returning migrants, tourists, or injecting drug users, infection during the 1990s appears to have taken place mainly within indigenous but narrow sexual networks, both heterosexual and homosexual, with expansion into the general population confined by the Islamic marital and social order, although it was under increasing strain.37
The spread of HIV in Nigeria needs to be seen in this context. It was often described as a delayed epidemic, ‘with a potential for rapid increase’, but in fact it fitted logically into broader West African patterns. Nigeria experienced two infections by HIV-1, one in the south caused mainly by CRF02_AG and the other in the north caused by CRF06_cpx. Both revealed their first HIV cases in 1986, in sex workers, among whom and their partners much of the early proliferation took place.38 In 1993 the first widespread sentinel survey showed prevalence of about 1.9 per cent among pregnant women. During the next six years it rose gradually to 5.4 per cent and the variation between different states widened, but those most affected were scattered broadly across the country. The highest prevalence (16.7 per cent in 1999) emerged in Benue state, in central Nigeria, where Aids was known as ‘the Abuja disease’. ‘No one suffers from this sickness in our village here,’ it was said, ‘but these women who go to Abuja [for commercial sex] suffer from it. They come home almost dead.’ Of 40 people with Aids studied in that village, only one did not have a history of ‘life abroad’. The next highest prevalence was 12.5 per cent in Akwa-Ibom state in the extreme south-east, where cross-border traffic coincided with great female independence and exceptionally high levels of commercial sex.39
Three reasons may help to explain why Nigeria did not suffer an explosive epidemic like that in Côte d’Ivoire. One was that Nigeria was too big and diverse, with many local epidemics but no primate city to transmit disease throughout the country. Rural prevalence was higher than urban in some states in the early 2000s. The second reason was that sex workers were mostly Nigerians and only marginally involved in the wider West African sex trade, at least until the later 1990s, so that even in 1994 only 13 per cent of sex workers in Lagos were infected. The third reason was the restraint imposed by the culture of the Muslim north, where women were commonly secluded and average HIV prevalence was significantly lower than in the centre and south-east.40 It is more difficult to explain why prevalence was even lower in the south-west, where extra-marital sex had long been common among the Yoruba and had become increasingly so among the young in the course of the twentieth century, unless perhaps the very diffuseness of partnerships rather than their concentration around high-risk sex workers gave protection.41 On the other hand, one factor encouraging the spread of disease was the mediocrity of Nigeria’s health system, rated by the World Health Organisation as one of the worst in the world. In 1995 the Federal Ministry of Health estimated that 10 per cent of HIV transmission was by blood transfusion, a problem still unresolved ten years later.42
In 1995, also, Nigeria’s health authorities estimated that at least 24 per cent of the country’s HIV infections were by HIV-2, although the country lay well outside the range of the sooty mangabey.43 The virus had probably entered Nigeria from the west at much the same time as HIV-1 was spreading from the east and south. Further west along the Guinea coast and in Senegambia, however, HIV-1 had to penetrate a region where HIV-2 was already endemic, if generally at low prevalence. The first search for HIV-1 in Senegal in 1985–6 chiefly revealed cases of HIV-2, both among sex workers in Dakar and especially in the southern Casamance region bordering the epicentre of the disease in Guinea-Bissau. Almost all were Senegalese who had never left the country, whereas the first HIV-1 cases identified were predominantly foreigners or Senegalese men who had travelled elsewhere in West or Equatorial Africa and often had histories of homosexuality or drug use. In 1990 Senegal’s national prevalence of HIV-2 was reckoned to be nine times that of HIV-1, but the greater virulence of the latter enabled it to overtake HIV-2 in 1996–7. By 2004 HIV-1 in Senegal was sixteen times more prevalent than HIV-2, which was of equal importance only in the Ziguinchor region on the Guinea-Bissau border.44 During the 1990s this reversal took place everywhere in the western coastal region except Guinea-Bissau, where the differential between the two infections narrowed but did not close, chiefly because of continuing (although declining) high levels of HIV-2 infection among older women.
Senegal gained international renown by limiting its national HIV prevalence at age 15–49 to little more than 1 per cent. Much of its infection was concentrated among the Jola people close to the southern border with Guinea-Bissau, where prevalence was two or three times the national average.45 Young, infected Jola migrants began to return from Côte d’Ivoire during the late 1980s to die at home. Like the Yoruba and many other young people throughout the continent, they had during the twentieth century adopted risky patterns of pre-marital sex in response to the commercialisation of the economy, the need to migrate for urban employment, the declining status of women consequent on the spread of Islam, the increasing difficulty of marriage, the collapse of customary sexual restraints, the spread of sexually transmitted diseases, the marginalisation of the region within independent Senegal, the destructive impact of structural adjustment policies, and their continuing anxiety to bear children at the peak of fertility.46 Elsewhere in Senegal, however, Muslim culture