FIGURE 1 Estimated global distribution of HIV-1 infections by region. Data are from the World Health Organization (1).

the Americas, AIDS has already become the leading cause of death for both men and women aged 15–49 years (24). It has been estimated that the HIV pandemic may have already resulted in the death of nearly 750,000 children worldwide and that, by the year 2000, 10 million children under 15 may be orphaned because of the premature death of HIV-1-infected mothers and fathers from AIDS (5). Overall infant and child mortality rates will increase as much as 30% more than previously projected as a direct consequence of perinatal HIV infection. Consequently, pediatric AIDS is now threatening much of the progress that has been made in child survival in developing countries during the past 20 years.

While the origin of HIV infection remains an enigma, several factors have been hypothesized to be responsible for the eventual spread of HIV. Historically, from retrospective serologic studies it is evident that HIV existed in humans as early as the late 1950s, although it did not become epidemic until nearly 20–30 years later (6). One hypothesis is that the migration of individuals from areas of low endemicity to new uninfected areas was eventually responsible for dissemination of HIV throughout the world. This was by no means a rapid event but probably occurred over a 40-year period. Unfortunately, because of the lack of vaccine or effective antivirals, it is inevitable that further dissemination will still occur from established indigenous transmission resulting in an escalation of the epidemic over the next decade. The World Health Organization now estimates that as many as 40 million people will be HIV-infected by the year 2000 (7).

This paper will review the conceptual issues regarding the migration of populations with its associated social changes in certain regions as a major force responsible for the eventual dissemination of HIV infections worldwide. Because data are limited on the frequency and size of



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