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Examining the connections between climate change and diarrheal disease

November / December 2011 | Volume 10, Issue 6

Woman walks through flooded street, water up to her ankles, 2-story wooden buildings on either side of street
Photo by Dr. Karen Levy

A new Fogarty-funded study in Ecuador examines
the link between climatic exposures and health,
and whether social and infrastructure factors can
mediate the impact.

By Jeff Gray

Rainfall, temperature and other climatic factors affect the transmission of diarrheal disease, which causes about 2 million deaths each year, mostly among children. Fogarty is funding a new project in Ecuador to study the complex relationship between climatic exposures on health and the extent to which social and infrastructure factors can mediate the impact.

The study, led by Dr. Karen Levy of Emory University, is one of nine initial projects funded by NIH's Human Health Impacts of Climate Change program. The new research initiative is administered by the National Institute of Environmental Health Sciences and is designed to explore how climate change will directly and indirectly affect human health risks.

Levy's study will bring together U.S. and Ecuadorian scientists with expertise in environmental epidemiology, modeling and prediction, tropical medicine and health impacts of climate change. The team will employ a novel approach, correlating data from five years of surveillance of diarrheal disease in 4,000 people living in 21 villages in rural Ecuador, weather pattern data for the same region dating back to 1965, and datasets on social and infrastructure conditions in the villages.

Wooden latrine immersed in shallow flood waters just feet from covered porch
Photo by Dr. Karen Levy

A flooded latrine in one of the villages to be
studied. Communities with poor sanitation are
often exposed to contamination from fecal
matter during flood conditions.

The third data component of the team's approach will be crucial, as the communities being studied vary greatly in terms of infrastructure and social conditions while the overall climate across the region is similar. According to Levy, flooded latrines from excessive rainfall can be one factor in spreading diarrheal disease pathogens. Infrastructure features such as piped water systems and sanitation coverage can all lessen the impact of rainfall and other climatic drivers of waterborne disease. The social circumstances and human responses of each community also play a critical but little-studied role in disease transmission.

"Rather than treating social conditions as noise in the analysis, we look to explain the uncertainty in climate-disease relationships by examining villages under the same climatic regime with differing social and infrastructure conditions, which we refer to as the social vulnerability of a community," said Levy. "Our approach provides a more complete understanding of the many ways - physiological, social and institutional - that climate affects disease incidence in communities."

The project will assess the studied communities' social vulnerability through existing ethnographic data - including interviews and observations collected over seven years - and additional fieldwork in the 21 villages. The resulting findings will allow Levy and her team to gauge their ability of the villages to adapt to both current and future climate change scenarios. The study outcomes will also be useful in determining the importance of social variables versus climate-related variables in the prevention of gastrointestinal disease, helping to shape effective health intervention strategies.

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