In work published over the past three years, Pascual and coworkers at the University of Barcelona and the International Center for Diarrhoeal Disease Research in Bangladesh found evidence that El Nino-Southern Oscillation (ENSO), a major source of climate variability from year to year, influences cycles of cholera. They looked initially at climate and disease data from Bangladesh for the past two decades; more recently they compared those results with data from Bangladesh for the periods 1893-1920 and 1920-1940 to see whether the coupling between climate variability and cholera cycles has become stronger in recent decades. Their examination of the data, which relied on a suite of techniques called time series analysis, suggests that it has.
"We had known that ENSO plays a role in the variability of cholera, but our work revealed that the role of ENSO has intensified," says Pascual, who was named one of "The 50 Most Important Women in Science" by Discover magazine in November 2002. What's more, the link is strongest during ENSO events, with cholera increasing after warm events and decreasing after cold events. In the years between events, the climate-cholera link breaks down.
With predictions that ENSO will become stronger and more variable in coming years under a global warming scenario, understanding how its connection to human disease changes will be increasingly important, says Pascual. Often, it's difficult to tell whether disease cycles are
Contact: Nancy Ross-Flanigan
University of Michigan