The inappropriate use of face masks has helped to blow the worldwide reaction to the SARS virus completely out of proportion, says John Oxford, professor of virology at Queen Mary, University of London. "They're totally useless in the way they're being used," he said. "They've not been used in the correct context, which is why the whole world's got inflamed and worked up," he told BioMedNet News.

The evidence now suggests that the 29,751-base pair coronavirus that causes SARS is pretty difficult to catch. "You only get it by coming face to face with someone with the virus," said Oxford. "You won't pick it up in the street," he said.

So, in Hong Kong, which has seen less than 2000 SARS cases in a population of around 6.75 million, you'd have to come into close contact with nearly 5000 people before you met one that might infect you, says Oxford.

Wearing masks was therefore only an appropriate precaution for those interacting closely with large numbers of people, he says. "Nursing staff, taxi drivers, and maybe hotel receptionists were the only ones that needed to wear one," he said. Nevertheless, the widespread use of masks in public places, has caused panic around the world.

"It's a very compelling and frightening image of these people who were hiding themselves behind masks from this disease," said Karin Wahl-Jorgensen of the School of Journalism, Media and Cultural Studies at Cardiff University, UK. "Imagery is always crucial, particularly with television. If you don't have good visuals, you don't really have a news story," she said.

"Certainly, the fact that you did have these frightened people running around with masks on did actually contribute to the moral panic resulting from SARS," said Wahl-Jorgensen.

The first major analysis of the epidemiology of this disease confirms that it is difficult to transmit. "It seems as if it probably requires close contact," said Asra Ghani of the department of infectious disease epidemiology at Imperial College, London.

The statistical analysis of available data from Hong Kong and China revealed that the number of deaths caused by SARS was very different in different age groups. The fatality rate was 13.2% for patients under the age of 60, but as high as 43.3% for those over the age of 60, report Ghani and colleagues in a recent article in The Lancet.

One unusual feature of this virus that has emerged from Ghani's research is that most people who get SARS do not infect anyone else. But some individuals, known as "superspreaders", appear to be responsible for transmitting the disease to dozens and sometimes hundreds of others, Ghani says. "I think it's becoming clear that superspreaders have some role [in disease transmission]," she said.

HIV is a classic case of such transmission heterogeneity, she adds. Most people have just a few sexual partners and so transmit the virus to one or two other individuals. But a small number of people have a large number of partners, which spreads the virus widely, she says.

The superspreader phenomenon could help explain the persistence of SARS. These individuals bump-up the rate of transmission and keep the infection going, says Ghani. "That can produce what's starting to look like an epidemic" from something that is actually quite difficult to transmit, she said.

But it is still not clear what makes someone a SARS superspreader. It is important to find out if these people have higher viral loads or more contacts than individuals who are not superspreaders, says Ghani.

Similarly, the origins of the virus remain a mystery. Media speculation that intensive livestock production was to blame was quashed earlier this month by Peter Roeder of the Animal Production and Health Division of the United Nations' Food and Agriculture Organization.

It is true that a high human population density in close contact with several species of intensively farmed livestock potentially provides a substrate for cross-species transmission, evolution, and amplification of many pathogenic agents, says Roeder. But in the case of SARS, he said, "There is currently no evidence for an origin in farm animals ... and it seems unlikely, even if the origin of the virus is still a mystery."

In spite of the very high rates of fatality caused by this enigmatic coronavirus, all indicators suggest that it will not kill as many people as more infectious viruses like influenza, concludes virologist Oxford. "I think the virus is telling us that it's not very dangerous," he said.

For example, the 1918 pandemic of "Spanish flu" is estimated to have killed only 2.5% of those that went down with the illness. But it was so infectious and spread so widely that by the end of the year, the death toll had topped 40 million. By contrast, since SARS emerged in the Guangdong province of China just over 6-months ago, it has claimed fewer than 1000 victims.

Nevertheless, there are still so many unknowns about SARS that we need to remain alert, says Oxford. "We think it took the 1918 flu epidemic a year to get going," he said, and we just don't know whether we are experiencing a lag before SARS gets cracking, he warned.