The world is preparing for a new natural disaster. As the deadly H5N1 bird flu spreads across the planet, scientists fear it could mutate into a highly virulent human disease. So far it has killed 165 humans, thousands and thousands of birds, a few cats and several tigers.

If this virus evolves the ability to spread from human to human the result could be global devastation on a scale that will make our annual flu epidemics look like a teddy bear's picnic.