The debate over the origins of Sars continues with a new theory from a Cardiff astronomer who believes that the virus could have fallen from space. Professor Chandra Wickramasinghe of the Cardiff Centre for Astrobiology, believes that life did not evolve out of primordial soup but that tiny organisms rained down during a violent comet storm 4bn years ago. He claims that up to a tonne of organisms still fall from the heavens every day. "On occasions we would expect to find pathogenic micro-organisms such as viruses coming down too," he says. The theory would explain why it started in China, where the Himalayas "prod" the atmosphere, making a weaker point of entry for bugs, with the east winds carrying it across China.

While scientists work around the clock to find out more about the cause, a cure and eventually a vaccine for Sars, preventative advice is starting to emerge. The consensus seems to be that washing your hands is the best way to prevent the spread. Jonathan Cohen, professor of infectious disease at Brighton and Sussex medical school, says that washing hands to prevent the spread of infection has been common practice since the 19th century. "In many ways what we are dealing here with Sars is typical 19th-century medicine - an outbreak of an infectious disease for which we have no treatment. The difference is that we have modern molecular techniques, which means a -vaccine is already being developed."

Sars is rapidly spreading on the internet. Half a million sites referencing it have sprung up since the outbreak began. The British Medical Journal this week reports on some of the offers you can get online. Young Again Nutrients says its supplement Beta Glucan can bolster the immune system, while Sars Research Laboratories offers a Sars travel kit containing masks, silver aromatic respiratory solution, ingestible colloidal silver, 10 pairs of latex gloves, silver skin liquid bandages and antiseptic handwash for $49.95. US authorities told the BMJ that consumers should be wary, and that companies could be "playing on fear".