Predicting a Pandemic

Scientists say the tropics is the next emerging disease hotspot.

According to a new study, countries along the equator, such as Southeast Asia, India and Bangladesh, West Africa, Southern Brazil and some parts of Europe and North America could be hotspots for the next pandemic disease.

During the past three decades, researchers have spent billions of dollars trying to detect and predict the seemingly random emergence of dozens of infectious pandemics. The cost to businesses caused by SARS alone is estimated to be between $50 billion and $100 billion. Now, a team of British and U.S. scientists say they can predict for the first time where the next major pandemic disease like HIV/AIDS or SARS could occur.

They point to any of a number of developing countries concentrated along the equator and encourage increased surveillance to prevent the spread of a potential outbreak. Regions like Southeast Asia, India and Bangladesh, West Africa, Southern Brazil, Europe and some parts of North America have the highest risks, they say.

"This is a seminal moment in how we study emerging diseases," says Professor John Gittleman, dean in the University of Georgia's Odum School of Ecology. "It's a really big deal to make these global predictions."

But this is not where Gittleman and Kate Jones, a senior research fellow at the Zoological Society of London, planned to end up when eight years ago they began looking at global patterns of animal extinction. Their original research studied which factors were likely to contribute to extinctions of large mammals and required assembling large computer databases to model and forecast extinctions. They took into account things like human population density, home-range sizes of animal populations and maps of geographic ranges of mammal species.

At that time, Jones began work with Peter Daszak, executive director of the Consortium for Conservation Medicine at Wildlife Trust, who was asking questions about global disease emergence.

"Peter worked on emerging diseases of wildlife, and we were interested in figuring out how to predict which wildlife species would be more at risk of emerging diseases," Jones recalled. "But data on emerging diseases in wildlife are very hard to get." The two wondered if the animal extinction forecasting models Jones and Gittleman had worked up could be used to predict human diseases.

It made sense. "We thought we would test the technique on one species we had good data for—humans," Jones said, and 3 years later, the researchers have a major breakthrough in understanding where and why pandemic diseases emerge.

The scientists analyzed 335 incidents from more than 50 years of disease emergence patterns and plotted the results on a global, "emerging disease hotspots" map. The map shows that the next new important zoonotic disease—one that originates in an animal—is likely to appear in the tropics, a region rich in wildlife species and under increasing pressure from people.

"We need to set up 'smart surveillance' in these hotspots—proactive monitoring that identifies the next HIV or SARS before it even emerges," said Daszak.

"After years of debate, the scientific community is now able to offer a convincing, predictive tool to help policy professionals and resource managers better allocate global resources in the fight against emerging diseases." says Rita Teutonico of the National Science Foundation, the federal agency that funded the work.

Using global databases and sophisticated computer models, Jones and her team have determined that zoonoses are the most current and important threat to humans. The research shows "the key threat to public health is where human population growth and wildlife diversity clash," said Daszak.

The study, published in the February 21 edition of the journal Nature, pinpoints regions of the world where human and animal encroachment is present, mostly developing nations. Most surveillance resources focus on the richer countries in the north, but according to the researchers, the data suggest some resources need to be redirected.

"Our priority should be to focus more surveillance in these developing countries," said Daszak. "If we continue to ignore this important preventative measure then human populations will continue to be at risk from pandemic diseases," he said.