Don't feed the bears

The BBC reports on a new and somewhat frightening study on emerging infectious diseases worldwide. Researchers from the Zoological Society of London (ZSL), and University of Georgia and Columbia University's Earth Institute analysed 335 emerging diseases from 1940 to 2004. Using computer models, they attempted to correlate emerging diseases with human population density or changes, latitude, rainfall or wildlife biodiversity, and then plotted the 'hotspots' for disease emergence on a global map. One surprise was the location of the hotspots. Instead of arising in northern industrialized nations -- with its better surveillance systems and (over)use of antibiotics -- new infectious diseases tended to spring from tropical Africa, Latin America and Southeast Asia. Another surprise is that the majority of emergent diseases are zoonotic pathogens, i.e. pathogens that leapt from animals to humans, and that of these zoonotic diseases, 72% came from wildlife, not domesticated animals. As we increase the earth's population, and increasingly encroach on wilderness areas, the probability of zoonotic transmission increases; once the pathogen has made the leap from animal to man, it then can spread fairly rapidly by international travel and trade. The SARS epidemic -- likely originating from horseshoe bats in rapidly industrializing China -- is a paradigm case for the future emerging epidemics.

Hopefully the results of the study will enable us to predict outbreaks. Now we only need to work on the man-made causes of these outbreaks, and the global inequalities in capacity to respond to the infectious disease epidemics that we partly dish out to ourselves.