Introduction Approximately 2.5 billion people are at risk from dengue. Climate change could drive the epidemic potential of this disease through temperature impacts on both the virus and the mosquito vector. We describe the past and present global distribution of transmission and estimate possible changes to dengue distribution arising from climate change.

Methods Two systematic reviews:

1. Geographically defined case reports, and

2. Models of climate change impacts on transmission

Results The current distribution of dengue is generally less extensive than historical limits but several countries have recently reported transmission for the first time. Over the past century, dengue has contracted in the southern states of North America, much of Australia, parts of Southern Europe and Japan, China and South Africa, most likely due to piped water supplies and removal of water storage, changes in housing conditions and vector control measures. Modelling studies consistently project increased climatic suitability for transmission this century and an expansion of the geographic regions at risk of dengue. An increase in temperature of just 1°C can substantially increase transmission potential.

Conclusion Existing models of transmission provide incomplete projections of disease risk as the geographic limits to transmission result from a complex interaction between physical, ecological and social factors which have not been explicitly included in current, linear models. Urban poverty (eg, poor housing quality and stored domestic water) remains an important promoter of dengue transmission in regions with favourable climate, while factors associated with prosperity (eg, surveillance and control measures) can limit transmission in climate-suitable areas.