factor—such as civil war, male circumcision, STDs, or rate of partner change—is simplistic. Instead, it appears that the simultaneous occurrence of several risk factors for HIV transmission determines how rapidly and to what level HIV spreads among a population and who becomes infected. This epidemiologic diversity not only reflects differences in sexual and other behaviors, but also suggests that the epidemic has not reached an equilibrium in most areas.

The HIV epidemic and the demographic structure of the population of sub-Saharan Africa will have complex interactions over time. The population is predominantly young, in sharp contrast with the age structure in developed countries, and many of the behavioral factors associated with HIV transmission are common among young people. Accordingly, the large number of people under age 15, who will soon enter their sexual and reproductive lives, represent a priority group for AIDS and STD prevention.

KEY RECOMMENDATION 1. Basic surveillance systems for monitoring the prevalence and incidence of STDs and HIV must be strengthened and expanded.

Good social science research is as dependent as public health and medical research on reliable and valid HIV/AIDS surveillance data. With the implementation of various interventions aimed at controlling HIV transmission, periodic monitoring of STD and HIV prevalence and incidence among selected populations is essential both for assessment of the impact of these programs and for decision making on program design and implementation.

Recommendation 3-1. More emphasis must be placed on HIV incidence studies for monitoring trends in HIV infection rates.

Although seroprevalence provides important information regarding currently infected individuals in an area, measuring incidence is also critically important for estimating the rate of change in the spread of HIV infection in a given population. In particular, data on current incidence provide the most direct and immediate information regarding the potential effects of a given intervention. Together, prevalence and incidence studies can provide information regarding the current status of the epidemic in terms of numbers of infected individuals and the rate of spread within a given population on an annual basis.

Recommendation 3-2. STD and HIV prevalence and incidence data should be combined with behavioral and demographic information.

Current surveillance systems are often limited, incomplete, and inconsistent, and they rarely measure behavioral or demographic variables. Given new, non-



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