Hong Kong researchers also said a SARS vaccine developed with their mainland Chinese counterparts was ready for testing on animals.
Yuen Kwok-yung, head of the University of Hong Kong's Department of Microbiology, said an activated strain of SARS coronavirus would be tested. Preliminary results will be known in six months, and there are no present plans for human testing, he said in a statement.
Toronto believed it had shaken severe acute respiratory syndrome after reporting the biggest outbreak outside Asia in April. But news emerged last week of the possible new cases, and officials acknowledged that Canada could have between 30 and 40 cases that went undetected.
The World Health Organization placed Toronto back on a list of SARS-affected areas Monday, but stopped short of advising travelers to avoid Canada's largest city. Toronto was removed from that list May 14.
The Toronto deaths, along with one in Hong Kong and three more in China, brought the worldwide death toll to 724. More than 8,100 people have been infected since the disease emerged in November, apparently in China's southern Guangdong province.
China, which has reported the most cases and deaths, reported just eight new cases Monday, its lowest reported daily increase to date. Taiwan reported 15 new cases.
Taipei's health chief, Chiu Shu-ti, resigned late Sunday night, taking the blame for last month's SARS outbreak at the capital's Hoping Hospital. The facility was the source for most of the island's SARS infections.
Chiu, known as an iron lady for her dedication to work and swift action, offered to quit soon after the city-run hospital was sealed off April 24 to contain infections. But Mayor Ma Ying-jeou asked her to stay. Chiu offered to resign again, saying the timing was right because the Taipei outbreak was coming under control.
"After a long talk, I decided to let her retreat from the front line," Taipei's mayor said.
Later Monday, two Japanese doctors arrived to study why SARS spread so quickly in Taiwan — an economically developed society similar to Japan's. Japan has no confirmed SARS cases but is concerned the virus will hit there next.
"We want to bring a message and say you are not alone," said visiting physician Hiroshi Noguchi of Narita Red Cross Hospital. "We are standing in the same boat."
The eight new cases announced in Toronto were linked to outbreaks at hospitals, and officials insisted there was no transmission of the disease to ordinary Canadians.
"We still see no evidence of community transmission of this disease," said Dr. Colin D'Cunha, chief medical officer of health for Ontario province.
One of the new cases was a 96-year-old man who died. Health officials said they believe the man was the index, or first case, of the new cluster. He was in North York General Hospital, where health officials say he may have infected health care workers, other patients and their family members in one ward in late April.
A patient transferred from the ward to St. John's Rehabilitation Hospital was considered the likely source of four more cases under investigation, they said.
Another 26 people have been listed as suspected SARS cases and about eight others could be suffering from the disease. The outbreaks led the United States to issue a travel advisory for Canada last week, a step short of advising against unnecessary travel there.
"We're still getting phone calls and it's disconcerting," said Dr. Donald Low, a key member of the SARS containment team in Canada. "And the examination of those phone calls leads to further (case) investigations. It's not over."
WHO has stressed it has no plans to reinstate a travel advisory for Toronto. Such an advisory was imposed April 23 but lifted a week later.
In Singapore, visitor arrivals fell by 73 percent in the first three weeks of May but the city-state's tourism chief predicted Monday that business will recover in June if there are no new SARS cases.
Singapore asked Monday that any illegal immigrants showing SARS symptoms come forward. They would be sent home but not charged under the city-state's strict immigration laws, Home Affairs Minister Wong Kan Seng said.
No illegal immigrant has yet been found with SARS, Wong said. Singapore has recorded 31 deaths from the 206 people infected.
The education ministry also told students to bring thermometers to their exams next month. Separate rooms will be set aside for students with mild fevers or who have returned from SARS-affected countries, the ministry said Monday.
Hong Kong reported one new death Monday and only one new infection over the weekend, bringing its death toll from SARS to 267. Health secretary Dr. Yeoh Eng-kiong also said Monday the families of three health care workers, including a doctor, who died of SARS will be given $385,000 each.
In China, volunteers and officials in Beijing handed out "spit bags" and tissue packets over the weekend, intensifying a public health campaign aimed at preventing the spread of SARS in the capital, where tens of thousands of people remain under quarantine.
Gobs of saliva are a common sight on the streets of Beijing, where at least 167 people have died of SARS and almost 2,500 people have been infected.