In 2002, 29.4 million people in Africa were estimated to be living with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS); 3.5 million were newly infected; and about 2.5 million died from AIDS (1). There are few studies on the natural history of HIV infection among African populations. One reason for this is that such studies require large numbers of individuals to agree to provide blood samples repeatedly so that the date of seroconversion can be identified. They must also agree to be under surveillance for 10 years or longer. Nonetheless, data on the natural history of HIV are essential for counselling patients, estimating the likely social and economic impact of the disease, planning health services, and guiding treatment strategies. This review brings together information on the natural history of HIV-1 and H1V-2 infections among adults in sub-Saharan Africa.
MEDLINE, EMBASE and PubMed databases were searched using the keywords "HIV" or "AIDS" and "natural history" and "Africa" and "adults." We excluded studies that only recruited patients according to specific opportunistic disease criteria.
Survival of individuals infected with HIV-1
The natural history of HIV-1 is well described in developed countries, where about 1.5 million people infected with HIV-1 are living with HIV/AIDS. Data from 38 cohort studies conducted in Europe on more than 13 000 people infected with HIV-1 with reliably estimated dates of seroconversion before the widespread use of highly active antiretroviral therapy (HAART) have been collated to estimate the median survival of individuals seroconverting at different ages (2). For those seroconverting between 15 and 24 years of age the median survival time (and 95% confidence interval (CI) was 12.5 years (95% CI = 12.1-12.9). For those aged 25-34, median survival was 10.9 (95% CI = 10.6-11.3). For those aged 35-44 it was 9.1 (95% CI = 8.7-9.5). And for those aged 45-54 years, the median survival was 7.9 (95% CI = 7.4-8.5).
The survival of people in Africa infected with HIV-1 from their date of seroconversion has been reported in only one study. This study was conducted by Morgan et al. in rural south-western Uganda (2). Among 168 incident cases, who were infected predominately through heterosexual contact and whose median age at seroconversion was 30 years, 44 individuals died. The median survival was estimated as 9.8 years (interquartile range 6.1--less than 10.3 years). This is about 1 year less than the median survival time of HIV-infected people in developed countries who seroconverted between the ages of 25 and 34 years before HAART was widely available (3). Although based on small numbers, there was some evidence in the Ugandan study that survival varied with age at infection: older patients tended to have shorter survival times. The age-standardized mortality rate of people infected with HIV-1 was 6.7 deaths per 100 person-years (which was 7.9 times higher than that for controls not infected with HIV). Participants had regular access to basic clinical care as part of the study including treatment with drugs that appear on WHO's list of essential drugs. However, in the rest of Africa the majority of people infected with HIV do not have regular access to care. It is unclear whether access to care had a major impact on survival. The authors report no difference in survival among 71 HIV-1 cases identified by serological testing during prevalence studies (seroprevalent cases) who were part of the research programme and 126 cases who were not invited to join the research study (2). It is also important to note that the size of the cohort in whom the date of seroconversion was known approximately (the sero-incident cohort) and the number of deaths were comparatively small and that no other sero-incidence survival studies among the general population have been conducted in Africa. …