So instead of analyzing long-term trends, Pascual and graduate students Mauricio Santos-Vega and Amir Siraj decided instead to compare malaria cases year-to-year, in two regions that had kept detailed records of the times and locations of infections. Working with colleagues at the University of London, the Oromia Regional Health Bureau in Ethiopia, and Columbia University in New York, they mapped the geographical distribution of malaria cases in the Antioquia region of western Colombia from 1990 to 2005 and the Debre Zeit area of central Ethiopia from 1993 to 2005 before intense intervention efforts had begun. For each region, they analyzed how distribution along elevation gradients changed from one year to the next, then looked for statistical associations to fluctuations in annual average temperatures.
Their analysis showed that the distribution of malaria cases shifted to higher elevations in warmer years. When temperatures cooled, the distribution of cases retreated to lower elevations.
Pascual and her colleagues also used their analyses to consider the increasing prevalence of malaria in Antioquia and Debre Zeit during the 1980s and 1990s, and found that changing temperatures could account for those long-term trends. "In those decades, we are already observing an effect of climate change," says Pascual.
The impact of ongoing climate change will be large, she says. In Ethiopia alone, 37 million people live at altitudes of 1,600 to 2,400 meters (5,249 to 7,874 feet), the range the team analyzed in their study of Debre Zeit. In a previous analysis, Pascual and colleagues estimated that without control measures, an increase in 1 degree Ce
|Contact: Jim Keeley|
Howard Hughes Medical Institute