HIV incidence and prevalence projections for Zimbabwe: Findings from five mathematical models

Introduction: Understanding how HIV epidemics are likely to behave in the future is key to informing HIV response strategies in low-income countries. Up-to-date HIV epidemiological estimates are important for policy decision- making, but surveillance data can be out of date. This study compared forecasts from HIV epidemiological models.Methods: Five independent modelling groups (EMOD-HIV, Goals, HIV Synthesis, Optima and PopART-IBM) calibrated their mathematical models to datapoints provided by the Ministry of Health and produced several indicators of the HIV epidemic in Zimbabwe for the period 1990 to 2040, under a status quo scenario in which it was assumed continuation of interventions at the current level.Results: All models predicted a continuous decline in HIV incidence and prevalence. However, there was variability in the estimated 2023 incidence rate (range: 2.0-3.3 per 1 000 person-years) and prevalence (range: 12.1%-14.3%). Variance was even larger in 2040 for incidence (range: 1.0-3.0 per 1 000 person-years), while this was not the case for prevalence (range: 3.9%-6.0%). All the models predicted that the country would reach a target of less than 7 800 new HIV infections per year by 2025.Conclusion: Five independent mathematical models fitted to the Zimbabwe Ministry of Health and Child Care's HIV surveillance data provided consistent predictions of continued decline in HIV incidence and prevalence in Zimbabwe if interventions continue to be implemented at the current levels, with prevalence predicted to be around a third of its level in 2000 by 2040.