The key to controlling the rapid but seemingly erratic spread of a lethal respiratory disease known as SARS could lie in identifying highly infectious people known as "super spreaders," a World Health Organization official said Saturday.
In an effort to solve the puzzle, a WHO team is visiting hospitals and talking with experts in the southern Chinese province of Guangdong, where the epidemic of severe acute respiratory syndrome began.
The four-member team is most interested in "the phenomenon of `super spreaders' -- people who seem to spread their disease to a lot of other people," said the WHO team leader, Dr. Robert Breiman.
Figuring out why they are so infectious "may lead to public health approaches that will be very effective for control," he said as new deaths were reported Saturday by Hong Kong and Malaysia.
Worldwide, SARS has killed at least 90 people and sickened 2,300 in more than a dozen countries. Symptoms include high fever, aches, dry cough and shortness of breath. No cure has been found.
In the largest outbreak of the disease outside of Asia, an eighth person died of the disease in Canada Saturday, and health authorities were investigating whether a ninth death was caused by the virus. All eight deaths have been in Toronto.
Aside from health care workers who caught SARS from patients, those infected have little in common, Breiman said.
Guangdong accounts for 40 of the 46 deaths reported in China. The first case was recorded in November and since then more than 1,100 people in the province have been sickened.
On Saturday, Vice Premier Wu Yi was quoted by state media as calling for a national disease warning system, with a focus on fighting SARS and "emphasis placed on a public health information system."
Wu's comments, carried by newspapers and the Xinhua News Agency, were the highest-level response yet to demands that the secretive communist government change its handling of such outbreaks. The report followed an extraordinary apology Friday by the country's top disease-prevention official amid international criticism that China released information too slowly.
In Thailand, which has suffered two deaths, Health Minister Sudarat Keyuraphan said he might call on military medics to help screen airline passengers for SARS.
Singapore, with six deaths, said its number of new infections was dropping. Authorities said people should resume their normal routines and that schools would reopen in the coming week.
Experts have linked SARS to a new form of coronavirus, other types of which usually are found in animals. But Chinese specialists say they found a rare airborne form of chlamydia -- a virus usually transmitted through sexual contact -- in many who died.
The finding has raised yet another question: Is the sickness caused by one virus or bacterium and made more lethal by another?
"If you have one pathogen and you get hit with, say, coronavirus, (do) you get a particularly bad disease?" Breiman said. "Or are you more likely to transmit? Do you become ... a `super spreader'?"
The WHO team, which includes specialists who work in the United States, Germany, Wales and Bangladesh, planned to stay in Guangdong through Tuesday.
On Saturday, they visited Zhongshan University in the provincial capital, Guangzhou, where experts have hundreds of blood samples and other material from people with the disease, also known as SARS.
The team is recommending that Chinese specialists re-examine such specimens to see "if there's evidence of not just one pathogen ... but a few of them," Breiman said.
Highlighting the seemingly selective nature of SARS was the first known case -- a businessman in his 40s from Foshan, an industrial city in Guangdong. He passed it to four people without infecting his own four children.
The man later recovered and was released from the hospital in January.
On Saturday afternoon, the streets of Guangzhou were teeming with cars, bicycles and shoppers.
Zhao Yan, a 20-year-old medical student, was out with a friend. Both had been worried when the outbreak peaked in February and people were buying up rice, oil, salt, white vinegar and Chinese medicine in a frenzy.
"We read about it in the paper, we heard about it from friends, we saw it on TV. We were worried," said Zhao, who used to wear layers of masks, especially when at medical facilities for class.
But now, she added, things have calmed down a lot. She no longer wears masks.
"We feel that if it's your turn to get sick, there's no way to escape."