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In the U.S., meanwhile, SARS is the only story other than the war in Iraq that has made it onto just about every news broadcast and front page. Even though nobody has died in the U.S. or even, with a single exception, got extremely sick, Americans are worried that this country could be the next major stop on SARS' international grand tour (see box), prompting President Bush to put SARS on the short list of quarantinable diseases last week.
All of this may seem like an overreaction to an illness that is not nearly as deadly as West Nile virus--SARS kills 3.7% of its victims, compared with West Nile's mortality rate of 6.7% last year--and evidently much less contagious than measles or even the flu. "It's the type of disease that seems to require a lot of direct close contact with somebody who's pretty sick," says Dr. Stephen Ostroff, deputy director of the National Center for Infectious Diseases at the Centers for Disease Control (CDC) in Atlanta.
But what makes SARS so frightening to scientists and the public is how much is still unknown about it, including where it came from, exactly how it spreads, how long its incubation period lasts (and thus how long a victim has been contagious when symptoms appear) and whether a vaccine will ever be available. Infectious-disease specialists are haunted by the great Spanish Influenza pandemic of 1918-19; it killed fewer than 3% of its victims but infected so many that at least 20 million people died in just 18 months--more than were killed in combat in World War I. And until health officials know for sure what they're dealing with, they tend to be overcautious. "When you confront new diseases and they begin to travel widely," says WHO spokesman Dick Thompson, "you have to do everything you can to try to stop the transmission."
If not for the secrecy of the Chinese government, health officials could have acted a lot earlier. It was back in November that a mysterious respiratory illness began spreading through the southern province of Guangdong. Officials hushed up the outbreak to prevent panic, and by February at least 305 Guangdong residents had developed SARS, according to Chinese officials. More cases are thought to have appeared in Beijing and other cities. By the time China finally turned in a two-page report to WHO a month later, the disease was already on the move.
In early March the illness landed in Hong Kong, where patients started showing up at the Prince of Wales Hospital. Hong Kong health officials have become particularly skilled at identifying respiratory diseases because the city is located so near the rich agricultural zones of southeastern China, where pigs, poultry and millions of people live in close proximity. Illnesses like influenza routinely jump from animals to humans, which is why new strains of flu often originate in Asia. Alert to the fact that something strange was going on, authorities in Hong Kong quickly notified WHO and began trying to determine how the disease arrived on the island and how it might be driven off.