"Climatic determinants" and simple thresholds for dengue early warning in Vietnam: a One Health perspective.

In recent years, dengue transmission in Vietnam has transitioned from predictable seasonality to climate-driven instability due to rising temperatures, urbanization, and hydrological extremes, among other factors. Traditional early warning systems based on case averages are becoming increasingly unreliable because of climate non-stationarity, resulting in both false alarms and missed warnings. This perspective summarizes available research on temperature, drought, rainfall extremes, diurnal temperature range, heatwaves, and El Niño anomalies, highlighting biologically-based thresholds that have been observed to precede outbreaks. We advocate for a pragmatic, hybrid early warning system that combines probabilistic national models with operationally simple meteorological triggers adapted to localized conditions. Integrating One Health factors, such as water storage practices, urban livestock habitats, and climate-sensitive vector control technologies, can facilitate optimal responses. This climate-informed, trigger-based approach helps to provide a realistic dengue control and prevention strategy that navigates low-cost and "no regrets" interventions in the face of accelerated environmental change.