Amid signs that patients thought to have recovered from SARS are experiencing relapses, doctors in Hong Kong ordered patients not to hug or kiss anyone for a month after their release from hospital in case they still carry the virus.
WHO says outbreaks of severe acute respiratory syndrome appear to have peaked in most places other than China, where more than 100 new cases of infection are recently being reported daily in Beijing alone.
Authorities said they had no idea when the capital's infection rate might subside.
To ease some pressure on the city's dramatically overloaded health system, they began transferring patients to a new SARS hospital. Ambulances with flashing blue lights dropped off the sick, then drove through a pool of disinfectant as they departed.
The complex of one-story prefab buildings, surrounded by a high brick wall next to an ostrich farm, was built in eight days by 7,000 laborers working around the clock.
At least 91 people have died of SARS and more than 1,640 have been sickened in Beijing, which has shut down schools for 1.7 million students, and closed cinemas, karaoke bars and other entertainment places.
Frightened Chinese villages have erected barriers and posted guards to protect their communities from possible SARS carriers. Millions of Chinese have obeyed government orders to stay home during current May Day holidays.
On Friday, officials said only healthy Beijing university students could go on vacation to their hometowns and that they must not travel to known SARS-affected areas and also stay away from underdeveloped rural areas and China's west, which lack a strong health care system.
In Hong Kong, health officials said some patients released from hospitals after they were thought to have recovered continue to carry the SARS virus, and some have suffered relapses.
Hong Kong health director Dr. Margaret Chan urged all recovered patients to be meticulous about hygiene.
"We warn them not to have close contact with family members, like no kissing, no hugging," said Dr. Joseph Sung, head of the Department of Medicine at the Chinese University of Hong Kong.
Doctors there say traces of the virus have been found in the urine and excrement of some people thought to have recovered, although there is no evidence of the disease having been spread by them.
One big outbreak in Hong Kong, at the Amoy Gardens apartment complex, is believed to have been spread partly through leaking sewage pipes, but involved people who were clearly sick with SARS.
University of Hong Kong microbiologist Yuen Kwok-yung said the virus thought to cause SARS could enter a lull during warm-weather months then pick up again in the winter.
Any such outbreak could be catastrophic in crowded Hong Kong if everyone is not "super-clean," he said in a radio interview. "If this new virus behaves like the two previous coronaviruses that were transmissible among humans, we have reasons to believe that we might have to a gasp for breath in summer.
There is no cure for SARS, which carries symptoms including fever, body ache, dry coughing and shortness of breath. However, most patients recover with prompt hospital care.
SARS has killed at least 418 people and sickened more than 5,900 worldwide. In developments elsewhere: