AIDS in Africa: an epidemiologic paradigm

THE ACQUIRED IMMUNE DEFICIENCY SYNDROME (AIDS) has become recognized as a global health problem. Cases have now been reported in 74 countries with more than 25,000 cases in the United States, nearly 3,000 cases in other countries of the Americas, more than 3,000 cases in Europe, and several thousand cases suspected and many more unrecognized in Africa (1,2). It is estimated that at least several million people worldwide have been infected with the causative agent, referred to as human T-lymphotropic virus type III (HTLV-III)/lymphadenopathy virus (LAV), or more recently as human immunodeficiency virus (HIV) (3). As many as 10 to 30% of these HIV-infected individuals may develop AIDS within the next 5 to 10 years (4-6). With the present lack of a curative therapy or vaccine, this disease now ranks as the most serious epidemic of the past 50 years. Although the immunopathogenesis of HIV infection is similar in most AIDS patients (7), the epidemiology and clinical features of the infection in different countries may vary, depending on cultural differences, endemic diseases, and other unidentified risk factors. In Africa, the different clinical features of AIDS and the difficulty in identifying the risk factors frequently associated with AIDS in the United States, such as homosexuality and intravenous drug use, have raised questions regarding the nature of the disease and the factors responsible for HIV dissemination in that continent (1,2,4). Here we review the epidemiologic and clinical features of AIDS in Africa and discuss the potential problems faced by public health officials in developing prevention and control strategies. Historical Perspective Shortly after the recognition of AIDS in the United States, cases of the disease were identified among Africans residing in Europe (8). Immunologically, these cases were identical to AIDS cases in the United States, with marked depression of CD[4.sup. +] lymphocytes (T-helper cells) and cell-mediated immunosuppression. Clinically, the African cases resembled Haitian AIDS cases with prominent gastrointestinal symptoms and opportunistic infections, such as oroesophageal candidiasis, cryptococcosis, toxoplasmosis, and mycobacterial infections (8-10). As of 31 March 1986, 177 cases of AIDS were reported among Africans residing in ten European countries (Table 1) (2). These cases originated from 24 African countries, mostly in Central Africa. In contrast to the European cases, African cases had a male to female ratio of 1.7:1, and 90% had no identifiable risk factors. Even among Europeans with AIDS and a recent history of travel to Africa, nearly 90% denied homosexuality or intravenous drug use. These unusual epidemiologic features prompted a series of investigations in 1983 to determine the pattern of AIDS in Central Africa. During a 4-week period, 38 patients with AIDS and 20 patients with AIDS-related diseases were identified in a large general hospital in Kinshasa, Zaire (11). Cases were equally distributed among men and women; females with the disease were younger and more often unmarried than male AIDS patients; and clusters of AIDS cases among men and women were linked by heterosexual contact. In a simultaneous investigation of 26 cases in Kigali, Rwanda, 43% of the female patients were identified as prostitutes (12). The fact that there was no evidence of homosexual transmission or intravenous drug use indicated that the pattern of AIDS transmission was different, and that heterosexual contact might be an important factor in transmission. Although the recognition of AIDS in Africa is consistent with the temporal occurrence of the disease in the United States and Haiti, several case reports and retrospective serologic surveys of banked sera have suggested that HIV infection may have occurred earlier in Africa (13-15). The earliest serologic response to HIV was found in serum collected from Kinshasa, Zaire, in 1959 (14). Sera from West and East Africa in the 1960's and early 1970's have also shown a high prevalence of weakly Positive specimens (for example, seropositivity in 1. …