Global map pinpoints disease 'hotspots'

BBC News 20 Feb 08;

A detailed map highlighting the world's hotspots for emerging infectious diseases (EIDs) has been released.

It uses data spanning 65 years and shows the majority of these new diseases come from wildlife.

Scientists say conservation efforts that reduce conflicts between humans and animals could play a key role in limiting future outbreaks.

Writing in Nature, they said their map revealed that global anti-EID resources had been poorly allocated in the past.

Researchers from the Zoological Society of London (ZSL), and the US-based University of Georgia and Columbia University's Earth Institute analysed 335 emerging diseases from 1940 to 2004.

They then used computer models to see if the outbreaks correlated with human population density or changes, latitude, rainfall or wildlife biodiversity.

Finally, the data was plotted on to maps to reveal the "hotspots" around the globe.

Healthy environment

"Our analysis highlights the critical importance of conservation work," said co-author Dr Kate Jones, a research fellow for ZSL.

"Conserving areas rich in biodiversity from development may be an important means of preventing the emergence of new diseases."

The researchers found that 60% of EID events were caused by "non-human animal" sources.

They add that 71% of these outbreaks were "caused by pathogens with a wildlife source".

Among the examples listed by the team was the emergence of Nipah virus in Malaysia and the Sars outbreak in China.

Others included the H5N1 strain of bird flu, Ebola and West Nile virus.

The number of events that originated from wild animals had increased significantly over time, they warned.

"This supports the suggestion that zoonotic EIDs represents an increasing and very significant threat to global health," the paper's authors wrote.

They added that it also highlighted the need to understand the factors that lead to increased contact between wildlife and humans.

"We are crowding wildlife into ever smaller areas, and human population is increasing," explained Dr Marc Levy, a global change expert at Columbia University's Earth Institute.

"Where those two things meet, that is the recipe for something crossing over."

He added that the main sources were mammals that were most closely related to humans.

'Missing the point'

While some pathogens may be picked up while hunting or by accident, others - such as Nipah virus - are transmitted to humans from wild animals via livestock.

Because humans had not evolved resistance to these EIDS, the scientists said that the results could be "extraordinarily lethal".

The main hotspots were located in low latitude regions, like South Asia and South-East Asia, which were not the financial focus of global funds to prevent the spread of EIDs.


"The world's public health resources are misallocated," opined co-author Peter Daszak, executive director of the Consortium for Conservation Medicine at the US-based Wildlife Trust.

"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."

However, Dr Dazak said that the maps were the first to offer a prediction of where the next new disease could emerge.

His colleague, Dr John Gittleman from the University of Georgia's Odum School of Ecology, described the data-set as a "seminal moment in how we study emerging diseases".

"Our study has shown that bringing ecological sciences and public health together can advance the field in a dramatic ways," he observed.

The researchers said that the priority should be to set up "smart surveillance" measures in the hotspots identified on the map.

Dr Daszak explained that logistically straightforward bio-security measures, such as screening people who come into contact with wild birds and mammals in the hotspot areas, could halt the "next Aids or Sars before it happened".

"It simply follows the old adage that prevention is better, and cheaper, than finding a cure.

"If we continue to ignore this important preventative measure, then human populations will continue to be at risk from pandemic diseases," Dr Daszak warned.