Seroepidemiology of HTLV-III antibodies in a remote population of eastern Zaire.

A human retrovirus--human T cell lymphotropic virus-III (HTLV-III)--has recently emerged as the probable cause of acquired immunodeficiency syndrome (AIDS). In May 1984, 250 outpatients at a hospital in a remote area of eastern Zaire were surveyed for AIDS type illnesses and the prevalence of antibodies against HTLV-III determined by an enzyme linked immunosorbent assay using disrupted whole HTLV-III virus as the antigen. No clinical cases of AIDS were diagnosed among these patients. Overall, 31 (12.4%) had clearly positive ratios (greater than or equal to 5.0) and a further 30 (12.0%) had borderline ratios (3.0- less than 5.0). Western blots of serum samples from subjects with antibodies yielded bands consistent with HTLV-III as found in American patients with AIDS and members of groups at risk of AIDS. The prevalence of antibody was highest in childhood (p = 0.02); among adults prevalence rose slightly with age. HTLV-III antibodies were more common among the uneducated (p = 0.006), agricultural workers (p = 0.03), and rural residents (p = 0.006), but the Western blot bands were generally weak in this group. By contrast, one urban resident had strong bands. The relatively high prevalence of antibodies among the rural poor in this area of Zaire suggests that HTLV-III or a closely related, cross reactive virus may be endemic in the region. A different natural history of infection, perhaps in childhood, may also explain the findings.