Much Higher SARS Death Rate Is Found

The death rate from SARS is substantially higher than many experts had previously believed, reaching 13.2% among young and middle-aged people, and as high as 55% among those over 60, according to the first major study of patients.

An international team of researchers studied the first 1,425 SARS patients in Hong Kong to reach the findings, published online Tuesday by the international medical journal the Lancet.

“I’m not surprised that it is higher among elderly people,” said Dr. Arthur Rheingold of UC Berkeley. “We would expect that for any respiratory disease, but 55% is quite alarming. This is a bad disease. That’s why we are so concerned about trying to prevent its further spread.”

By comparison, while the study provided no overall SARS death rate, the normal mortality rate for pneumonia caused by other viruses and bacteria is just under 11% overall, with a higher rate among the elderly. Smallpox kills nearly a third of its victims, anthrax can kill more than half and AIDS can kill nearly all. Influenza, in contrast, kills less than 1% of its victims, but it is much more readily transmitted from person to person.

Two other, smaller studies released Tuesday found somewhat different results, suggesting that the course of the disease can be highly variable.

A study of the first 144 SARS patients in Toronto released online by the Journal of the American Medical Assn. found an overall death rate of 6.5%, but noted that the risk of death was three times as high for patients with diabetes and 2.5 times as high for those with other serious conditions.

And a study by physicians at Tan Tock Seng Hospital in Singapore of the first 20 patients there showed an overall death rate of 16.7%.

The World Health Organization had initially reported that the death rate from severe acute respiratory syndrome was about 2.5% to 3%, but infectious disease experts have always considered such low numbers an unrealistic artifact of the way WHO calculated the numbers. In essence, WHO simply counted the number of deaths and divided that by the number of cases, said epidemiologist Lone Simonsen of the National Institute of Allergy and Infectious Diseases.

“It takes at least 10 days to die of a SARS infection,” she said. “That means there is a lag factor that has not been factored into the calculations.”

In fact, the new data from the Hong Kong study show that the average time between admission to the hospital and death is 36 days, so it has taken some time for the real number of deaths to become apparent.

Many suspected cases of SARS, furthermore, have been eliminated as researchers have developed better diagnostic tests for the disease -- further increasing the apparent death rate.

The study was conducted by a team led by Dr. Roy Anderson of Imperial College London, and included physicians from Hong Kong University, the Chinese University of Hong Kong, and Hong Kong health authorities.

Anderson cautioned that the findings were based only on hospital admissions. If there are substantial numbers of people who contracted the virus without developing symptoms or did not get sick enough to enter the hospital, the actual death rate could be lower, he said.

The team found that the time between recognition of symptoms by a patient and admission to a hospital was initially about five days, but that it dropped to three days during the period covered by the study. Earlier admission to hospitals did not affect the outcome of the disease, they found, but did reduce the risk of transmitting the virus to other people. The average hospital stay for those who recovered was 23.5 days.

They also found that the incubation period averaged about 6.5 days, but could be as long as 14 days -- 40% longer than health officials had previously believed. Most quarantines now last only 10 days, which may be too short, Anderson said.

The team also concluded that public health measures instituted by Hong Kong authorities had a major impact on controlling the outbreak. In the first stages, the number of cases was growing exponentially, they said, but by April 28, when they ended the study, the rate was down below 20 per day.

Hong Kong had nine new cases Tuesday, and eight each of the preceding two days. The city has now had 1,646 SARS cases and 193 deaths. There are 495 victims still hospitalized, including 73 in intensive care. The city has not exported a SARS case to another country for several weeks, said Dr. Yeoh Eng-kiong, secretary for Health, Welfare and Food.

WHO spokesman Dick Thompson noted that the fatality rate is lower in places where the outbreak has ended or is nearing an end. “We know that in a real situation where the outbreak has completed itself from beginning to end -- in Hanoi, Vietnam -- they had an 8% case fatality rate,” he said.

That is similar to the situation in Canada, according to the new study prepared by a team led by Dr. Christopher Booth of the University of Toronto. They studied the first 144 patients to contract the disease in Toronto and concluded that 77% of the infections occurred in hospitals. Canada has now had 346 confirmed SARS cases and 23 deaths.

Of the eight patients who died during the course of the study, six had diabetes and one had cancer, they found.

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Times staff writer Rosie Mestel contributed to this report.