This NYT report gives ground for a pessimistic view about SARS, but has some credibility problems. It begins:

The death rate from SARS may be significantly higher than health officials had thought, up to 55 percent in people 60 and older, and up to 13.2 percent in younger people, the first major epidemiological study of the disease suggests.

Mortality rates are bound to change somewhat as an epidemic continues. But unless the numbers fall drastically, SARS would be among infectious diseases with the highest death rates. Until now, fatality rates reported by the World Health Organization had ranged from 2 percent, when the epidemic was first detected in March, to 7.2 percent.

The new findings come from a statistical analysis of 1,425 patients suspected of having SARS who were admitted to Hong Kong hospitals from Feb. 20 to April 15. Over all, their mortality rate was estimated to be as high as 19.9 percent. By contrast, the influenza pandemic of 1918, which killed tens of millions of people worldwide, had an estimated mortality rate, over all, of 1 percent or less.

Let’s look at the last number. If a disease that kills ten million people has a mortality rate of 1 per cent, the number infected is 1 billion. The report is inexact, but clearly implies that several times that many people were killed and that the mortality rate was below 1 per cent. The world population in 1920 was less than 2 billion.

Obviously something is wrong here. This doesn’t mean that the estimates quoted about SARS are wrong, but it would be useful to have a better baseline for comparison.