China's authorities have introduced rigorous measures to curb the virus
Thousands of Sars investigators have been deployed in the Haidian district of China's capital Beijing, which has been worst hit by the disease, in a desperate bid to stop its spread.
The 30,000 investigators will check businesses and residences throughout the area looking for victims and ensuring that measures are being taken to improve hygiene, district official Zhou Liangluo said.
Each household in the district of 2.2 million people has been issued with a thermometer and emergency contact numbers, while offices and businesses have been ordered to install temperature-monitoring systems.
Known death tolls:
Mainland China: 348
Hong Kong: 298
Source: WHO/local authorities
Prime Minister Wen Jiabao has warned that it is of vital importance to prevent the disease spreading in the country's rural areas where so far there has not been a large epidemic.
"Sars prevention in vast rural areas is a key component of the fight against the disease," Mr Wen told the country's senior provincial officials on Tuesday.
"Neglecting prevention work in the rural regions will not be tolerated," Mr Wen was quoted as saying by the People's Daily newspaper.
In an unusually frank assessment of China's rural health care system, Mr Wen admitted that technical capabilities were poor in rural areas and epidemic surveillance systems unsound.
The BBC's Rupert Wingfield-Hayes in Beijing says that in many parts of rural China the health care system has simply collapsed and there are growing signs that the battle to keep Sars from spreading there is already being lost.
Meanwhile the World Health Organisation (WHO) has announced it is sending a team to the northern Chinese province of Hebei, where the number of Sars cases had risen sharply during the past week.
A WHO official said it was hoped that the team could help prevent a major outbreak in the densely-populated province.
The WHO has warned that the disease has not peaked yet in China, which on Tuesday announced 138 new cases, bringing the total to 4,409 and reported eight more deaths, taking the toll to 214.
In other developments:
Taiwan reports on Wednesday two more Sars deaths, raising the island's toll to 13.
Health officials in Singapore - which has the world's third-highest Sars death toll - say on Wednesday they need 10 more days to declare that the epidemic is under control.
Police in Beijing detain four people for spreading rumours about Sars on the internet and through mobile phone messages, Chinese Xinhua news agency reports.
The United States pledges to increase technical assistance to China to spread the spreading of Sars outbreak.
Miss Universe organisers in Panama say all contestants must have certified medical documents before they can take part in the pageant.
Deadlier than thought
Meanwhile a new study of the flu-like virus - the first to be based on a statistically sound sample of 1,425 cases - has discovered that the death rate among sufferers is much higher than previously estimated.
The WHO initially estimated that the death rate from the virus was 5%, but the study, conducted in Hong Kong, says one in five people has died from the disease (20%).
We have not seen a peak in China yet. We still have a considerable size of outbreak in Hong Kong
Gro Harlem Brundtland, WHO head
European Union health ministers, along with their counterparts from 10 candidate countries, have drawn up a set of proposals to tackle the global spread of the virus.
At a meeting in Brussels, they agreed to closer co-operation between member states on the prevention and control of communicable diseases and to make passengers arriving from infected countries complete a questionnaire.
But they backed away from a proposal to medically screen travellers for signs of the disease, saying that any action had to be balanced and proportionate to avoid stirring up unnecessary public fear.