WHO Director General Margaret Chan recently described climate change as the “fifth horseman” of the Apocalypse who will rain pestilence and disease upon humanity. She is concerned that rising global temperatures will lead to catastrophic death and destruction in the poorest countries of the world, and that “tropical” diseases like malaria and dengue will make their way northwards to Europe and America.

As G8 leaders gather in Tokyo, how seriously should they take Dr Chan’s warnings?

According to medical entomologist Prof Paul Reiter of the Institut Pasteur in Paris, bodies such as the WHO and the Intergovernmental Panel on Climate Change (IPCC), are promulgating a misleading and alarmist interpretation of the relationship between vector-borne diseases and temperature.

The reality is that the epidemiology of these diseases is a highly complex interplay of the ecology and behaviour of both humans and vectors that defies simplistic analysis. The resurgence of many of these diseases is a major cause for concern, but it is facile to attribute it to temperature: the principal determinants are politics, economics and human activities.

If the WHO, IPCC and other authoritative bodies continue to misuse science, policies will be enacted that will be both ineffective and counterproductive.