Climate change is occurring as a result of warming of the earth’s atmosphere due to human activity generating excess amounts of greenhouse gases. Because of its potential impact on the hydrologic cycle and severe weather events, climate change is expected to have an enormous effect on human health, including on the burden and distribution of many infectious diseases. The infectious diseases that will be most affected by climate change include those that are spread by insect vectors and by contaminated water. The burden of adverse health effects due to these infectious diseases will fall primarily on developing countries, while it is the developed countries that are primarily responsible for climate change. It is up to governments and individuals to take the lead in halting climate change, and we must increase our understanding of the ecology of infectious diseases in order to protect vulnerable populations.