Deadly animal diseases poised to infect humans

Jeremy Laurance in the Independent (UK) summarizes some recent work on zoonotic diseases: The world is facing a growing threat from new diseases that are jumping the human-animal species barrier as a result of environmental disruption, global warming and the progressive urbanisation of the planet, scientists have warned. At least 45 diseases that have passed from animals to humans have been reported to UN agencies in the last two decades, with the number expected to escalate in the coming years.

Dramatic changes to the environment are triggering major alterations to human disease patterns on a scale last seen during the industrial revolution. Montira Pongsiri, an environmental health scientist at the US Environmental Protection Agency in Washington, says that previous transitions in human history have had a devastating impact in terms of the spread of disease. "We appear to be undergoing a distinct change in global disease ecology. The recent emergence of infectious diseases appears to be driven by globalisation and ecological disruption," Dr Pongsiri said.

He and eight colleagues examined five emerging and re-emerging diseases – malaria, lyme disease (spread by ticks), Hantavirus (spread by mice and rats), West Nile disease (spread by mosquitoes), and schistosomiasis (spread by freshwater snails). They argue that changes in land use, farming practices and climate lie behind the increasing number of outbreaks.

…Dr Pongsiri and colleagues say that the number of people who succumbed to infectious diseases plummeted in the developed world during the industrial revolution, but the rise of manufacturing and pollution levels increased the incidence of chronic diseases including cancer, allergies and birth defects. Now, we are in the grip of another epidemiological transition driven by the destruction of plant and animal habitats, the loss of species and changes that have brought more humans into closer contact with animals than at any stage in human history, they say in the journal Bioscience.

…The behaviour of these new viruses is unpredictable – scientists don't know how likely they are to jump the species barrier into humans. But with more of them circulating, there is a higher chance of this happening, Dr Slingenbergh said. Flu viruses are getting closer to people and food, and agriculture practices are to blame. He said: "There is no evidence to suggest this is going to end any time soon. Agriculture looks set to continue growing for another two decades, and we are only at the beginning of climate change."…

Transmission electron micrograph of Sin Nombre virus, also known as hantavirus