Two decades of cholera in Dhaka, Bangladesh: Epidemiology, seasonal patterns, and environmental risk, insights from 2004-2024.

Cholera remains a critical public health challenge in Dhaka, Bangladesh, influenced by complex environmental and demographic drivers. This study analyzed around 20 years of 2% surveillance data (2004-2024) from icddr,b (n = 37,361) to investigate long-term trends and climatic associations using distributed lag non-linear models (DLNMs). Climate data (temperature, rainfall, humidity) were obtained from NASA's Earth Data archives. Findings reveal a significant demographic shift, with adults (>18 years) accounting for 65% of the 6,141 confirmed cholera cases. Seasonality was pronounced; 48% of cases occurred during the pre-monsoon period. While incidence peaked between 2004 and 2008, a recent resurgence was noted from 2019 to 2024. Environmental analysis showed a positive association between temperature and cholera risk, with relative risk (RR) rising from 0.75 at 20°C to 1.10 at 40°C. Precipitation emerged as a major driver, with risk peaking at 150 mm (RR = 1.5), high humidity (90%) also correlated with increased risk (RR = 1.10). The high burden among adults necessitates age-inclusive interventions, including targeted vaccination and WASH measures. Integrating climate data into early warning systems and expanding surveillance to informal settlements are vital for future outbreak prediction and control.