Technical Abstract: Climate has a demonstrated impact on infectious diseases and increased disease transmission has been linked to the El Niño/southern Oscillation (ENSO) phenomenon. The Climate Prediction Center of the National Oceanic and Atmospheric Administration has recently issued an unscheduled El Niño advisory, indicating that warm sea surface temperatures across the Pacific basin may have pronounced impacts on global tropical precipitation patterns. Knowledge of the demonstrated links between infectious diseases, particularly those transmitted by insects, and climate can allow us to forecast the risk of an epidemic or epizootic. Ocean temperatures have increased significantly in the last 2 months. Last month, drier-than-average conditions have been observed across all of Indonesia, Malaysia and most of the Philippines. High probability for above normal rainfall is indicated in central and eastern equatorial Pacific Islands, the Korean Peninsula, the U.S. Gulf coast and Florida, northern South America and equatorial Africa. The development of El Niño conditions will likely lead to extremes in climatic events, with above normal rainfall and flooding in some regions and drought in other regions. Current observations and forecast information indicate that the following regions are at increased risk for disease outbreaks: Indonesia, Malaysia, Thailand and most of the southeast Asia Islands for increased dengue fever transmission and increased respiratory illness; Coastal Peru, Venezuela, Colombia for increased risk of malaria; Bangladesh and coastal India for elevated risk of cholera; East Africa for increased risk of a Rift Valley fever outbreak and elevated malaria; southwest USA for increased risk for hantavirus pulmonary syndrome and plague; southern California for increased West Nile virus transmission; and northeast Brazil for increased dengue fever and respiratory illness. The current development of El Niño conditions has significant implications for global public health. Extremes in climate events with above normal rainfall and flooding in some regions and extended drought periods in other regions will occur. Forecasting disease is critical for timely and efficient planning of operational control programs. In this paper we describe developing global climate anomalies that suggest potential disease risks that will give decision makers additional tools to make rationale judgments concerning implementation of disease mitigation strategies.