Malaria and Global Warming in Perspective?

To the Editor: I read with great interest the article "From Shakespeare to Defoe: malaria in England in the Little Ice Age" (1). Unfortunately, the article is not as balanced as a presentation last year by Paul Reiter, which clearly illustrated that, although climate is important in the transmission of malaria, the influence of other factors (e.g., access to medical care and improved housing) is likely to be of more importance in Europe.

Malaria indeed was quite common in Europe, even in the Roman Empire and in Medieval Europe, and until a few decades ago, it was still present in parts of Europe, Australia, and North America. In fact, the failure of the 1806 British invasion of Zeeland in the Netherlands may be attributable to infection of the British forces with malaria. However, the authors referenced by Reiter have never made the claim that in the coming years warmer "temperatures will result in ma]aria transmission in Europe and North America." On the contrary, the reports of the Intergovernmental Panel on Climate Change Reiter quotes conclude that "Although climate change could increase the potential transmission of malaria [in Europe and North America], existing public health resources--disease surveillance, surface water management, and treatment of cases--would make reemergent malaria unlikely" (2,3).

Reiter's argument that some scientists attribute the recent observed increase in malaria risk to climate trends is also not accurate. While acknowledging the sensitivity of the malaria mosquito and parasite to climate, these researchers examine insect and incidence data to explore multiple factors underlying malaria emergence. Another group of scientists uses mathematical simulation models to estimate changes in malaria risk over the next few decades. These models, which are heuristic tools not meant to predict future worlds, assess how potential risk for malaria may by affected by changes in climate (4). The goals of both types of research are to improve knowledge of the complex malaria transmission cycle, define epidemic-prone areas, identify the reasons for increased malaria risk, and develop solutions to protect vulnerable communities.

Dr. Reiter acknowledges the sensitivity of malaria to climatic influences, and I am sure that he agrees that change in climate will affect risk for transmission--he may be skeptical as to whether global warming will ever become a fact, but that is another question. While Reiter's paper offers an interesting perspective on the history of malaria in Europe, it provides no illuminating information on the influence of climate change on human health.

References

(1.) Reiter P. From Shakespeare to Defoe: malaria in England in the Little Ice Age. Emerg Infect Dis 2000;6:1-11.

(2.) Intergovernmental Panel on Climate Change. The regional impacts of climate change: an assessment of vulnerability. Working Group II. Intergovernmental Panel on Climate Change. New York: Cambridge University Press; 1998. Chapters 5, 8.

(3.) Intergovernmental Panel on Climate Change. Climate change 1995: impacts, adaptations and mitigation of climate change: scientific-technical analyses. Working Group II, Intergovernmental Panel on Climate Change. New York: Cambridge University Press; 1996. Chapter 18.

(4.) Martens P. Health and climate change: modelling the impacts of global warming and ozone depletion. London: Earthscan Publications Ltd.; 1998.

For Reiter's response, please see http://www.cdc.gov/ncidod/EID/vol6no4/reiter.htm

Pim Martens Maastricht University, Maastricht, the Netherlands