Trends the Future Burden of Visceral Leishmaniasis in Afghanistan, Iran, and Pakistan: A Regional Epidemiological Modeling Study

Abstract

Background: Visceral leishmaniasis (VL) remains one of the world’s most severe neglected tropical diseases, causing substantial morbidity and mortality in low-resource settings. Despite regional control efforts, the disease persists as a major health challenge in the Middle East and South Asia. We aimed to estimate and forecast the sex-specific and national burden of VL in three neighboring countries of Afghanistan, Iran, and Pakistan through 2040.

Methods: To estimate the future prevalence of VL we applied an illness–death model using sex-specific data from the Global Burden of Disease 2021. Historical data from 1990–2021 were used to calibrate the model and forecast national trajectories of VL prevalence to 2040.

Results: In 2023, Afghanistan had the highest age-standardized VL prevalence (0.0176), followed by Iran (0.0159) and Pakistan (0.0093). Projections indicate strikingly divergent trends by 2040: prevalence is expected to rise to 0.045 (95% CI: 0.03–0.08) in Afghanistan and 0.211 (95% CI 0.10–0.45) in Pakistan representing increases of 156% and over 2,100%, respectively while Iran is projected to experience a sustained decline to 0.002 (95% CI: 0–0), an 87% reduction compared with 2021. These patterns are consistent across both sexes, though male prevalence remains roughly twice that of females.

Conclusion: Afghanistan’s decline likely reflects under-detection due to health system fragility, while Pakistan’s surge may result from both improved surveillance and genuine spread. Iran’s continued reduction demonstrates the impact of sustained public health investment. Strengthening surveillance and incorporating health system indicators into predictive models are crucial for accurate projections and effective regional control.