Increase in New Emerging Disease

Conservation of Wildlife May Prevent Emerging Diseases NEW YORK, New York, February 20, 2008 (ENS) -

Deadly emerging diseases have roughly quadrupled over the past 50 years, according to new research by an international team of scientists who have mapped the outbreaks' main sources. New diseases originating from wild animals in poor countries are the greatest threat to humans, the scientists warn.
These diseases spread to humans who move into shrinking pockets of biodiversity and have contacts with wildlife there.
Kate Jones, an evolutionary biologist at the Zoological Society of London and first author of the study, said the work 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.
"We are crowding wildlife into ever smaller areas, and human population is increasing," said coauthor Marc Levy, a global change expert at the Center for International Earth Science Information Network, an affiliate of Columbia University's Earth Institute. "The meeting of these two things is a recipe for something crossing over."
This is the first map that shows where pathogens passed from wildlife to humans. The lowest occurrences are green, the highest are red. (Image courtesy Nature)
The main sources of these emerging diseases are mammals, the scientists have learned. Some pathogens may be picked up by hunting or accidental contact. Others, such as Malaysia's Nipah virus, go from wildlife to livestock and then to people.
Humans have evolved no resistance to diseases that move from animals to humans, called zoonoses, so these diseases can be extraordinarily lethal. The scientists say that the more wild species in an area, the more varieties of pathogens they may harbor.
The HIV/AIDS pandemic, thought to have started from human contact with chimpanzees, has led to over 65 million infections; recent outbreaks of SARS originating in Chinese bats have cost up to $100 billion. Outbreaks like the African ebola virus have been small, but deadly.
Despite three decades of research, previous attempts to explain these seemingly random emergences have been unsuccessful.
In the new study, researchers from four institutions analyzed 335 emerging diseases from 1940 to 2004, then converted the results into maps correlated with human population density, population changes, latitude, rainfall and wildlife biodiversity.
Some 60 percent of the diseases traveled from animals to humans and the majority of those came from wild animals. With data corrected for lesser surveillance done in poorer countries, "hot spots" jump out in areas spanning sub-Saharan Africa, India and China; smaller spots appear in Europe, and North and South America.
"This is a seminal moment in how we study emerging diseases," said University of Georgia professor John Gittleman, dean of the Odum School of Ecology, who developed the approach used in analyzing the global database. "Our study has shown that bringing ecological sciences and public health together can advance the field in a dramatic way."
About 20 percent of known emergences are multidrug-resistant strains of previously known pathogens, including tuberculosis. Richer nations' increasing reliance on modern antibiotics has helped breed such dangerous strains, said Peter Daszak, an emerging diseases biologist with the Consortium for Conservation Medicine at the Wildlife Trust, who directed the study.
Daszak said that some strains, such as lethal variants of the common bacteria e. coli, now spread widely with great speed because products like raw vegetables are processed in huge, centralized facilities. "Disease can be a cost of development," he said.
The group's analyses showed that more diseases emerged in the 1980s than any other decade, likely due to the HIV/AIDS pandemic, which led to other new diseases in the immune-compromised victims.
In the 1990s, insect-transmitted diseases saw a peak, possibly in reaction to rapid climate changes that started taking hold then. Team members soon hope to study this possibility and its future implications.
Daszak says the study has immediate uses. "The world's public-health resources are misallocated," he said. "Most are focused on richer countries that can afford surveillance, but most of the hotspots are in developing countries. If you look at the high-impact diseases of the future, we're missing the point."
Team members say nations must share more technology and resources in hotspots to reduce risk. "We need to start finding pathogens before they emerge," said Daszak.
The study appears in the February 21 issue of the scientific journal "Nature." The research was funded by the U.S. National Science Foundation, an NSF/NIH Ecology of Infectious Diseases award from the John E. Fogarty International Center of the National Institutes of Health, and by three private foundations - The New York Community Trust, The Eppley Foundation and the V. Kann Rasmussen Foundation.
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