Peril From The East

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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 brief 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 such as influenza routinely jump from animals to humans, which is why new strains of flu often arrive from 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.

The pieces fell into place fairly rapidly. Of the first 45 people to contract SARS in Hong Kong, most had contact with employees of the Prince of Wales Hospital or family members of patients. Those people, in turn, had contact with a smaller circle who treated or visited a 26-year-old male patient, originally diagnosed with a nonspecific fever. That man, Hong Kong authorities determined, had stayed on the ninth floor of the Metropole Hotel in the Hong Kong district of Kowloon in February.

They also discovered that six other people who had stayed on the same floor of the hotel between Feb. 12 and March 2 had SARS too. One of them was a doctor, 64, from Guangzhou, the capital of Guangdong. Could he be the original cause of all the Hong Kong cases? "We believe this hypothesis is justified," says Dr. Margaret Chan, Hong Kong's director of health. At least one other Guangdong man took SARS with him to Spain, while several Metropole victims fanned out across the world to Singapore, Vietnam and Canada; people infected by them in turn spread the disease even farther afield.

I don't want to give anybody a false expectation that this is under control. — Stephen Ostroff, Centers for Disease Control

Once they realized what was going on, officials at who issued its unprecedented alert and, along with the CDC and other disease labs, launched an impressively coordinated effort to understand the illness as quickly as possible. By examining the victims' body fluids, pathologists at the University of Hong Kong determined that the probable culprit was a mutated coronavirus, although some victims also seem to be carrying a type of paramyxovirus, a member of the family that causes measles. It could be a helper virus that makes the coronavirus more virulent, or it could be an unrelated co-infection. For now, says who's Thompson, "we're proceeding as if we know it's the coronavirus for certain." Both the CDC and Hong Kong University are developing laboratory diagnostic tests for the virus and its antibodies to replace the much less accurate symptom-based diagnoses being used today.

Medical detectives are also trying to understand exactly how SARS is spread. The illness appears to infect the lower lobes of the lungs (unlike common-cold viruses, that typically attack the throat and nasal passages). That's not a good thing: viruses rising up from the lungs tend to be distributed in fine aerosols and thus travel farther than the relatively large droplets expelled in sneezes and bronchial coughs. "The data we've heard certainly don't suggest that aerosol transmission is common," says the CDC's Ostroff, "but we keep an open mind to that possibility."

Still, the large number of cases in Hong Kong's Metropole Hotel and Amoy Gardens apartments suggests to Thompson that "there is something going on, a form of transmission that we don't understand." Researchers are concerned that at least some victims — the Chinese doctor at the Metropole and someone in Amoy Gardens, perhaps — are so-called superspreaders. For unknown reasons, some people pass the virus along much more easily than most, perhaps because of the way they cough or the types of contact they have with others or because they carry an unusually heavy load of the virus. Says Ostroff: "We have not seen superspreading in the U.S., but it's a theory that has been advanced in both Canada and Asia." Kwan Sui-chu Kwan, the woman who carried SARS from Hong Kong to Canada, is believed to have infected as many as 155 people.