One study found that about 20 percent of the people hospitalized with the disease in Hong Kong are dying from it, while more than half of those over 60 die.
Nearly 200 of the more than 1,600 people believed to have the respiratory disease in Hong Kong have died.
Worldwide, the World Health Organization, which is leading the effort to stop SARS' spread, says the death rate ranges from 6 percent to 10 percent, depending on location. The U.S. Centers for Disease Control and Prevention puts the rate at 6.6 percent.
In Canada, where patients have been older, the death rate is 15 percent, said WHO spokesman Dick Thompson.
"What we do see is that in people under 40 the death rate is generally lower and in people over 60 the numbers are much higher," Thompson said.
A study conducted by scientists at Imperial College in London, the University of Hong Kong and the Hong Kong health authorities, estimated that the death rate could be as high as 55 percent in people over the age of 60.
In younger people — those under 60 — the death rate could be as low as 6.8 percent, the study found.
"It appears that people who are dying appear to be older with some significant underlying disease," says Dr. James Hughes of the Centers for Disease Control.
Dr. Mark Denison of Vanderbilt University, one of only a handful of corona virus experts in the country, says the relationship between age and illness or death could be crucial.
Early indications are that children seem to be spared the worst symptoms of SARS, raising the possibility that early infection could lead to later immunity.
"Examples in the past may have been viruses like measles that caused bad disease in adults who've never seen it, but caused a moderately serious disease in children," says Denison.
Still, Denison is the first to admit, the corona virus "mutates as a hobby," and the data is too preliminary to draw conclusions from.
"Everything about this virus has surprised me," he says.
Health officials continue to be surprised – and delighted – by the fact that the United States has been spared; to date the books show 65 cases and no deaths.
Some attribute it to extremely aggressive measures on a local public health level – things like quarantining aircraft and banning summer school students from Asian countries.
Some calls those precautions extreme; others say they are wise.
"As long as there's SARS transmission ongoing anywhere in the world it remains an issue for us in the United States," says CDC Director Dr. Julie Gerberding.
The new studies back that up, finding that the only thing that can stop SARS on its global trek is continued hyper-vigilance.
In other SARS developments: