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Feb. 22, 2008

Scientists Make First Map of Emerging Disease Hot Spots
Growing Threat Seen In Human-Wildlife Conflict, Drug Resistance

A new study provides the first scientific evidence that deadly emerging diseases have increased steeply and maps the outbreaks’ main geographic and host sources. The researchers say that although historically a majority of new infectious diseases emerged in wealthy countries, the future risks are high in many poor areas. The study appears in the Feb. 21 issue of Nature.

Map of wildlife zoonotic hotspots Map of zoonotic pathogens from wildlife, shown
from lowest occurence (green) to highest (red)

(Click image to enlarge)

Columbia researcher Marc Levy, deputy director of the University’s Center for International Earth Science Information Network (CIESIN), part of the Earth Institute at Columbia University, is a co-author of the study. According to Levy, data from the NASA Socioeconomic Data and Applications Center (SEDAC), which is operated by CIESIN, helped create a picture of disease hot spots around the world. Factors such as population density, population changes, latitude, rainfall and wildlife biodiversity were correlated with emerging diseases data from 1940 to 2004. This mapping of data formed a predictive picture of emerging disease hot spots in rich as well as poor nations, with implications for further prediction and prevention.

Related Links

University Launches New Climate Center, Columbia News, Jan. 24, 2008

Study Finds Emerging Diseases on Rise, NPR, Feb. 21, 2008

Major Disease Outbreaks Around World Becoming More Common, Guardian (U.K.), Feb. 21, 2008

“Overlaying maps of where the zoonotic (animal-borne) diseases have occurred, with population maps, allowed a pattern of relationships to emerge,” said Levy. Understanding these relationships “is a first step in prediction” and can lead to better surveillance and health care responses.

Emerging diseases—defined as newly identified pathogens, or old ones moving to new regions—have caused devastating outbreaks already. The research shows that disease emergences have roughly quadrupled over the past 50 years. Some 60 percent of the diseases traveled from animals to humans, and the majority of those came from wild creatures. With data corrected for lesser surveillance done in poorer countries, hot spots jump out in areas spanning sub-Saharan Africa, India and China, as well as smaller spots in Europe, and North and South America.

Some pathogens may be picked up by hunting or accidental contact; others, such as Malaysia’s Nipah virus, go from wildlife to livestock, then to people. Humans have evolved no resistance to zoonoses, so the diseases can be extraordinarily lethal. The scientists say that the more wild species in an area, the more pathogen varieties they may harbor.

“We are crowding wildlife into ever-smaller areas, and human population is increasing,”  said Levy. “The meeting of these two things is a recipe for [diseases] crossing over.”

In this study, CIESIN, which specializes in data and information management and research related to human interactions in the environment, contributed what is the centerpeice of the study: knowledge of the drivers of global environmental change and spatial demographic data.

Map of wildlife zoonotic hotspots Map of drug-resistant pathogens, shown from lowest occurence (green) to highest (red)
(Click image to enlarge)

“CIESIN played a leadership role in developing a methodology that identifies the statistical relationship between the drivers of diseases and disease patterns,” said Levy. “In terms of policy implications, we hope that the study will serve as the basis for increased surveillance and early warning. We can identify changes in pathogens in animal populations and get ready for the possibility that these pathogens may jump over to humans.”

The director of the study, Peter Daszak, an emerging diseases biologist with the Consortium for Conservation Medicine at the Wildlife Trust, another Earth Institute affiliate, says that some strains, such as lethal variants of the bacteria e. coli, are now spread with great speed because products like raw vegetables are processed in huge, centralized facilities. “Disease can be a cost of development,” he said. In rich nations, emerging disease outbreaks are also a result of multidrug-resistant pathogen strains caused by the overuse of antibiotics.

Kate E. Jones, an evolutionary biologist at the Zoological Society of London (ZSL) and lead author of the study, said the work also urgently highlights the need to prevent further intrusion into areas of high biodiversity. “It turns out that conservation may be an important means of preventing new diseases,” she said.

In addition to the ZSL and Earth Institute researchers, the study was co-authored by John L. Gittleman, dean of the Odum School of Ecology at University of Georgia.