Russia mulled tough border restrictions with China, where experts say the SARS epidemic has yet to peak despite tough measures, including crackdowns on Internet rumor mongers and on doctors who refuse to treat the infection.
Beijing police said dogs, cats and other pets of quarantined people will be isolated or killed out of fear they might be carriers.
The United States promised to work closer with China on SARS, although a senior Chinese official was noncommittal about providing American scientists with biomedical specimens from patients.
At least 497 people have died around the world, with 11 new fatalities in Hong Kong, five in China and two in Taiwan reported on Wednesday.
More than 6,800 have been infected since the disease surfaced in China's southern province of Guangdong in November.
New findings in Britain's Lancet medical journal show that SARS is killing one in five patients hospitalized with the virus in hard-hit Hong Kong, including 55 percent of infected patients aged over 60. In younger patients, the death rate could be as low as 6.8 percent.
"That's sadly still very high for a respiratory infection," said Roy Anderson, an epidemiologist at London's Imperial College who headed the study. "In other common respiratory infections it is much less than 1 percent in the vulnerable elderly."
The research — conducted with the University of Hong Kong and Hong Kong health authorities — is the first major study of SARS trends, but was based only on data from Hong Kong, where at least 204 people have died.
Scientists and agencies differ over what an average person's chances worldwide are of dying of SARS. The U.S. Centers for Disease Control and Prevention puts the overall death rate at 6.6 percent. WHO says it ranges from 6 percent to 10 percent.
In Hong Kong on Wednesday, masked health workers and weeping government officials attended the funeral of a nurse who was the territory's first medical professional to die after treating SARS patients. Lau Wing-kai, 38, died April 26 and was hailed as a "people's hero."
Severe acute respiratory syndrome continues to hit China despite mass quarantines, roadblocks, travel restrictions and some school shutdowns. There has been some progress, though. The number of new cases reported Wednesday, 159, was below 200 for the fourth consecutive day.
A WHO investigative team is to travel Thursday to the densely populated northern province of Hebei, where the number of SARS infections has doubled to 98 between April 30 and May 4.
Hebei province borders Beijing — which has been the worst affected by the SARS epidemic.
Chinese authorities fear SARS has the potential to devastate poor populations in the country's hinterlands.
"SARS prevention in vast rural areas is a key component of the fight against the disease," Premier Wen Jiabao was quoted as saying by the official Xinhua News Agency. "It is vital to the health of farmers, to rural economic and social development and also to the overall success of the anti-SARS battle."
In the northeastern Liaoning province, two doctors had their licenses revoked, Xinhua reported. One refused to see patients with fevers. The other would not attend meetings on SARS prevention. In the southwestern Sichuan province, one doctor was fired for refusing to treat suspected SARS patients, the agency said.
In Beijing, four people have been detained for allegedly trying to trigger panic with false rumors about SARS via the Internet and mobile phone text messages, Xinhua said.
Rumors have swept the Chinese capital in recent weeks, their impact increased by official reluctance to release information in the early days of the SARS outbreak.
Xinhua said three people in eastern Xuancheng city were charged with attacking police who tried to enforce a SARS quarantine order on one of their relatives.
SARS fears are affecting activities around the planet.
Organizers of the Miss Universe pageant said contestants must produce health certificates before the contest, scheduled for June 3 in Panama City. Models visiting from Hong Kong wore decorated surgical masks on the catwalk in at a Sydney fashion show.
In Taiwan, authorities ordered the closing and disinfecting of a big department store if a cashier with SARS-like symptoms is diagnosed as a positive case.
In the Philippines, Roman Catholic Cardinal Jaime Sin ordered priests to prevent "mass hysteria" over SARS. Last month, Sin urged the faithful to receive communion wafers by hand instead directly in the mouth, and discouraged people from the common practice of kissing public religious statues.
Russia's top health official recommended restrictions along the Chinese border.
"Only Chinese citizens should be allowed to leave and only Russian citizens should be let in," Gennady Onishchenko told Echo of Moscow radio, in remarks shown on Russian television.
U.S. Secretary of Health and Human Services Tommy Thompson said Chinese Vice Premier and Health Minister Wu Yi agreed to cooperate in training and lab development while more U.S. health advisers would go to China.
Thompson said that in a telephone call Monday night, Wu was noncommittal when asked if China would give U.S. experts specimens from Chinese patients at various stages of infection.
The U.S. Centers for Disease Control and Prevention downgraded its travel advisory against nonessential travel to Singapore to a travel alert. It downgraded its travel advisory for Vietnam on Monday.
A Singapore health official said the city-state will declare its SARS outbreak under control if no more new cases are found in the next 10 days.