Introduction The Greater Mekong Subregion (GMS)—spanning Cambodia, the Lao People's Democratic Republic (PDR), Thailand, Viet Nam, and areas in the southern part of the People’s Republic of China—is highly exposed to climate-sensitive health risks. Its tropical climate and ecology already create favourable conditions for vector-borne diseases, such as dengue and malaria, while floods, heat, and water insecurity continue to affect public health outcomes across the region. Climate change is compounding these pressures by expanding mosquito habitats, lengthening transmission seasons, and increasing the likelihood of outbreaks and other infectious disease risks. At the same time, more intense floods and heat extremes are straining sanitation, infrastructure, and health services, especially for poorer and more exposed groups. In this context, climate-informed early warning can help shift public health action from reactive outbreak response to anticipatory preparedness. By combining climate and environmental information with routine surveillance, early warning systems can identify periods of elevated disease risk early enough for health authorities to act before cases surge. However, skilful prediction alone will not protect communities. The real test is whether warnings and surveillance triggers lead to timely decisions and practical action, making this issue directly relevant to Sustainable Development Goals 3 (Good Health and Well-Being), 13 (Climate Action), and 16 (Peace, Justice and Strong Institutions). Analysis Climate-informed early warning is becoming more feasible. The case for climate-informed early warning in health is well established. Dengue transmission is shaped by climatic conditions, especially rainfall and temperature, and these relationships can provide lead time for public health action. Across the GMS, governments and partners are increasingly using seasonal outlooks, environmental indicators, and routine surveillance data to identify periods of elevated risk before health systems come under acute strain. This reflects a broader shift from reactive toward anticipatory action. Cambodia and the Lao People’s Democratic Republic (Lao PDR) illustrate this transition. Both countries are strengthening broader multi-hazard early warning systems and exploring how health can better integrate into national warning frameworks. In the Lao PDR, climate information is being linked with District Health Information Software 2 (DHIS2)-based health reporting to support dengue forecasting and related risk analysis. Cambodia has strengthened epidemic surveillance and is using forecasting approaches to support dengue preparedness and climate-resilient health planning. These developments show that the technical foundations for anticipatory action are increasingly in place. The real gap is between warning and action. This distinction reflects the standard early warning system value chain: risk knowledge (the foundation), monitoring and forecasting (the detection), dissemination and communication (the warning), and preparedness and response (the action). Forecasting risk is part of the chain, but early warning only becomes useful when information moves through the full sequence and leads to action. Evidence from the broader dengue literature supports this point: the World Health Organization's Early Warning and Response System is most effective when warnings trigger timely and sufficiently strong measures; where response is weak or delayed, the value of the warning sharply reduces. For this reason, effective early warning systems for health depend on seven operational ingredients: Coordinated multi-sector governance Climate-sensitive disease risk cuts across institutions. Health ministries manage the health sector response, but meteorological agencies generate climate information, local governments support community action, and disaster management systems often provide coordination structures. Multi-sector governance must establish mandates, routines, and a recognized forum where risk information is interpreted and translated into decisions. In practice, this can be supported by governance products such as memoranda of understanding, joint technical working groups, agreed roles and responsibilities, clear decision authority, and escalation pathways that define how alerts move from technical assessment to operational action. Data sharing and integration Epidemiological, meteorological, and hydrological information may all exist but not in formats that support integrated analysis and decision-making. The Lao PDR’s efforts to connect climate information with health data show the importance of interoperability, routine exchange, and a shared evidence base for decision-making. Because health data can be sensitive, data sharing should also be supported by clear governance arrangements, including agreed standards, privacy safeguards, access rules, and protocols for responsible use. Clear protocols and trigger-action plans Standard operating procedures should define alert levels, decision thresholds, and the actions linked to each level of risk. Trigger-action plans help institutions manage uncertainty by agreeing in advance what level of evidence is sufficient to justify a proportionate response. For example, wetter-than-normal rainfall outlooks, rising dengue cases, and increased mosquito abundance could trigger intensified vector control, community messaging, stock checks, and health facility readiness planning. Communication and community engagement Even technically sound systems can fail if warnings do not reach those who need to act, or if they are not trusted. Rural and remote health teams need messages that are clear and operationally meaningful, while communities need advice that is simple, credible, and linked to practical protective action. A people-centred approach should also consider equity, including local language, disability access, gendered access to information, older people, and trust in the messenger. The last mile is especially important in rural or high-risk areas, where local volunteers, radio, schools, and community leaders may be more effective than formal digital platforms. Resources and financing for preparedness Early action depends on whether supplies, staff, transport, and contingency funds can be mobilized quickly. Sustainable systems require financing mechanisms that support pre-agreed action, including preparedness stocks, surge arrangements, and budget pathways that can be activated early. Early warning system performance can fail when operations and maintenance are unfunded, even where the technical system is well designed. Continuous capacity building and adaptation Early warning is not static. Staff need training to interpret forecasts, use decision tools, communicate risk, and implement response measures. Institutions also require feedback loops, including post-event reviews to assess what worked, what did not, what should change before the next season. Routine review builds institutional memory and allows systems to improve over time. Quality assurance and evaluation Early warning systems should be assessed not only by the technical skill of the forecast, but also by whether they support timely and effective action. Useful measures include lead time, sensitivity and specificity, clarity of triggers, actionability for decision-makers, reach to vulnerable groups, and evidence that warnings help reduce avoidable cases, service disruption, or strain on health systems. Early warning is ultimately an institutional capability. Taken together, these seven elements point to a broader lesson: the challenge in early warning for health is not prediction alone but the systems needed to act on it. Models, surveillance, and digital tools all matter, but their value ultimately depends on whether institutions can turn foresight into timely, authorized, and properly resourced action. Climate-informed early warning can help health systems prepare for increased demand, protect routine services, and reduce peak pressure during outbreaks or climate-related events. Dengue provides a practical starting point for building the warning-to-action systems that health services will increasingly need as climate risks grow. Implications The opportunity is to support better forecasting and help countries translate technical progress into systems that are practical, scalable, and embedded in routine public health decision-making. Investments in climate data, surveillance, modeling, and digital platforms are already creating a stronger foundation for anticipatory action. The next step is to reinforce institutional arrangements that allow these tools to deliver value in practice, including coordination across sectors, trigger-based protocols, communication pathways, financing for early action, and workforce capability. To be effective over time, climate-informed health early warning needs to be embedded in routine sector planning, with clear mandates, recurrent resourcing, and arrangements for ongoing operation and maintenance. Development partners can make a particularly strong contribution by helping connect health, meteorological, and disaster management institutions; improving data-sharing and interoperability; strengthening warning-to-action protocols; and building capacity at subnational levels, where many early decisions are implemented. In practical terms, this means supporting joint meteorological-health working arrangements, trigger-action standard operating procedures, escalation pathways, and budget mechanisms that allow early action to be activated before impacts escalate. There is clear scope to facilitate regional learning across the Greater Mekong Subregion, where shared climate patterns, dengue risk, and common implementation challenges create a strong basis for exchanging experience and adapting good practice. Early warning for health is a practical entry point for strengthening climate-resilient health systems and improving how institutions manage risk under changing climatic conditions. This supports SDG 3 by strengthening preparedness and protecting service continuity, SDG 13 by enabling earlier adaptation, and SDG 16 by improving coordination and institutional responsiveness. Note: This Insight is part of regional technical assistance on Health Cooperation in the Greater Mekong Subregion, the team appreciates review comments from Anna C. Orquiza, ADB Disaster Risk Management team, Climate Change and Sustainable Development Department. Resources Asian Development Bank. Regional Technical Assistance: Increasing Investments in Early Warning Systems to Strengthen Climate Disaster Resilience. Asian Development Bank. 2025. Climate-Resilient Health Development: High-Level Health Care Climate Action Principle #1. ADB Sustainable Development Working Paper Series. No. 108. World Food Programme. 2025. Cambodia Launches National Roadmap to Save Lives with People-Centered Early Warning Systems. News Release. 20 November. World Health Organization and Ministry of Health, the Lao People’s Democratic Republic. 2025. Health National Adaptation Plan (H-NAP) for Building Climate Resilient Health Systems in Lao People’s Democratic Republic, 2025–2030. Ask the Experts Andrew Magee Climate Scientist Dr. Magee specializes in climate and disaster risk, resilience, and decision-making under uncertainty. Working across Asia and the Pacific, he supports early warning, adaptation, and climate-resilient planning, including for health systems, by translating climate science into practical information for preparedness and action. He holds a PhD from the University of Newcastle, Australia, where he is also an Adjunct Lecturer. Follow Andrew Magee on Nilandone Senvanpan Technical Specialist, Department of Communicable Disease Control, Ministry of Health, Lao People’s Democratic Republic Dr. Senvanpan is a medical doctor with a master’s degree in Tropical Medicine and International Public Health from the University of Health Sciences in the Lao People’s Democratic Republic. She has expertise in communicable disease control, health security, and regional health cooperation, contributing to cross-country coordination and technical engagement in the Greater Mekong Subregion. Ly Sovann Director of Communicable Disease Control Department, Ministry of Health, Cambodia Dr. Ly Sovann is Director of the Disease Control Department and advisor to Cambodia’s Ministry of Health. He also serves as Ministry spokesperson, IHR Focal Point, and Chair of the AMR Working Group. His expertise spans disease surveillance, outbreak investigation, public health emergency response, and pandemic preparedness and response. Thepphouthone Sorsavanh Chief of Statistics and Digital Health Division, Ministry of Health, Lao People’s Democratic Republic Dr. Sorsavanh has a background in health information systems, statistics, and digital health. He leads national efforts on health data and digital transformation within the Lao PDR’s Ministry of Health. Vasoontara S. Yiengprugsawan Senior Universal Health Coverage Specialist (Service Delivery), Human and Social Development Office, Sectors Department 3, Asian Development Bank Dr. Vasoontara Yiengprugsawan oversees ADB's health technical assistance, including noncommunicable diseases and mental health and regional cooperation in the Greater Mekong Subregion and BIMP-EAGA. She has held senior health research positions in Australia, a WHO Fellowship with the Asia Pacific Observatory on Health Systems and Policies, and worked in policy and research with a UN Migration Agency in Geneva. She holds a PhD in Epidemiology from Australian National University and an MA in International Development from Syracuse University. Follow Vasoontara S. Yiengprugsawan on Asian Development Bank (ADB) The Asian Development Bank is a leading multilateral development bank supporting sustainable, inclusive, and resilient growth across Asia and the Pacific. Working with its members and partners to solve complex challenges together, ADB harnesses innovative financial tools and strategic partnerships to transform lives, build quality infrastructure, and safeguard our planet. Founded in 1966, ADB is owned by 69 members—49 from the region. Follow Asian Development Bank (ADB) on Leave your question or comment in the section below: View the discussion thread.