Climate change, including climate variability, has multiple influences on human health. Direct impacts include the consequences of more frequent and intense heat waves, floods, and windstorms. Potentially larger impacts are likely to result from indirect mechanisms; climate can affect health through alterations in the geographic range and intensity of transmission of vector-, tick-, and rodent-borne diseases and food- and waterborne diseases, and changes in the prevalence of diseases associated with air pollutants and aeroallergens. Climate change could alter or disrupt natural systems, making it possible for diseases to spread or emerge in areas where they had been limited or had not existed, or for diseases to disappear by making areas less hospitable to the vector or the pathogen. The World Health Organization (WHO) estimates that climate change may already be causing over 150,000 deaths per year. Despite the increasing understanding of health risks associated with climate change, there has been limited identification and implementation of strategies, policies, and measures to protect the health of the most vulnerable populations. The countries in which this project will perform were chosen because of different priority vulnerabilities to climate change so that the results of the project will be directly relevant to decision-makers in other vulnerable countries. To facilitate learning, the UN agencies involved will ensure that best practice experiences are shared across countries and regions.