STRATEGIES FOR LIMITING THE SPREAD OF HIV IN DEVELOPING-COUNTRIES - CONCLUSIONS BASED ON STUDIES OF THE TRANSMISSION DYNAMICS OF THE VIRUS

Possible interventions to reduce the spread of human immunodeficiency virus (HIV) include actions that attempt to alter sexual behaviour, su ch as education aimed at reducing the rate at which individuals acquir e new sexual partners, and methods that reduce the probability of tran smission between partners, such as the promotion of condom use and the treatment of so-called ''cofactor'' sexually transmitted diseases. A mathematical model of HIV transmission that is able to mimic different approaches to the control of HIV transmission is employed to study th e relative values of different approaches, either used in isolation, o r in combination. The nonlinear nature of the term that describes the per capita rate of transmission dictates that for a given degree of in tervention, the benefit accruing in terms of reduced HIV spread depend s on the prevalence of infection before the introduction of control. B enefit is greatest when HIV prevalence is low. Combination approaches are predicted to be effective but the outcome is less than would be ex pected on the basis of simply summing the benefits resulting from each type of intervention used in isolation. The success of targeted inter ventions, aimed at those with high rates of sexual partner change, dep ends on the heterogeneity in levels of sexual activity within populati ons and what proportion of the population HIV is able to establish its elf in. Targeted interventions are predicted to be very cost effective but their overall success in reducing HIV spread by a significant deg ree depends on the timing of their introduction (within the time frame of the development of the epidemic) and the pattern of mixing between different risk groups or sexual activity classes.