Malaria rise in Africa parallels warming trends

New analysis challenges results of previous research

Researchers from the Johns Hopkins Bloomberg School of Public Health, the Tyndall Centre for Climate Change Research at the University of East Anglia, the Earth Institute at Columbia University, and other institutions conclude that the increase in the incidence of malaria in East Africa parallels warming trends over the last several decades. The new findings challenge the results of a study, “Climate change and resurgence of malaria in the East African highlands,” which was previously published in the journal Nature. The original study, conducted by researchers from the University of Oxford, found “no significant changes” in long-term climate. The new analysis is published in the December 12, 2002, edition of Nature.

“Weather data is particularly sparse in East Africa, and the climate database used was originally created to pool information for analysis over large geographic areas. There is potential, therefore, for reaching spurious conclusions when using such climate data to study diseases at the local level,” said Jonathan Patz, MD, MPH, lead author of the new analysis and assistant professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. He further added that, “Malaria is one of the world’s most climate-sensitive diseases, and the African Highlands is an area of key importance for climate-malaria risk studies.”

According to Dr. Patz and his colleagues, the previous study interpolated climate values to study locations at diverse elevations, differing on average by 575 meters, or approximating a 3 degrees Celsius temperature deviation. Dr. Patz and colleagues argue that the approach crucially ignored temperature variability, particularly essential within an area of such large altitudinal contrasts.

“The climate dataset used is not designed to reveal climate trends for specific locations. It’s appropriate for up-scaling information to African regions, not down-scaling to small area locations. It cannot support the type of analysis performed in the previous study,” explained Mike Hulme, PhD, co-author of the new analysis and executive director of the Tyndall Centre for Climate Change Research, School of Environmental Sciences, at the University of Anglia in Norwich, UK.

The new analysis found a mean warming trend of 0.15 degrees Celsius per decade from 1970 to 1998 across the same East African region included in the previous study.

“Reliable assessment of the long-term malaria/climate relationship requires better local monitoring of appropriate climate and disease variables to attain databases that can support long-term trend analysis. Moreover, processes as diverse as climate and human disease require researchers from different fields to work together in order to best assess health implications of long term past climate trends or future climate change,” said Dr. Patz.

“Regional warming and malaria resurgence” was written by Jonathan A. Patz, Mike Hulme, Cynthia Rosenzweig, Timothy D. Mitchell, Richard A. Goldberg, Andrew K. Githeko, Subhash Lele, Anthony J. McMichael, and David Le Sueur. It is published in the December 12, 2002, edition of Nature.

“Climate change and the resurgence of malaria in the East African highlands” was written by Hay SI, Cox J, Rogers DJ, Randolph SE, Stern DI, Shanks GD, Myers MF, and Snow RW. It was published in the February 21, 2002, edition of Nature.

News releases from the Johns Hopkins Bloomberg School of Public Health are available at www.jhsph.edu/Press_Room.

For further information on the Tyndall Centre for Climate Change Research, visit the Centre’s website at www.tyndall.ac.uk or contact Annie Ogden, UEA Press Office at 44-160-359-2764 or press@uea.ac.uk.