China has taken strict measures to try to control Sars
New research into the deadly Sars virus suggests it might be able to be spread through contact with contaminated objects.
World Health Organization (WHO) scientists say they have found that the pneumonia-like virus is more resilient than first thought, being able to survive for four hours on surfaces and up to four days in human waste.
Sars (Severe Acute Respiratory Syndrome) can also live indefinitely in sub-zero temperatures although it can be killed off even when doused in a detergent commonly used to sterilise contaminated areas.
The research backs up the theory that leaking sewage pipes helped spread an outbreak in a Hong Kong apartment block, in which 300 people were infected.
Known death tolls:
Mainland China: 348
Hong Kong: 298
Source: WHO/local authorities
Densely-populated Hong Kong has been badly hit by the virus.
Five new deaths and eight new cases were reported on Sunday, pushing the death toll there to 184.
In mainland China, the health ministry on Sunday reported seven new deaths and 163 new infections. It takes the death toll to 197.
Sars has killed nearly 450 people worldwide.
Most people catch Sars through coughing and sneezing.
But tests carried out by laboratories in China, Hong Kong, Japan and Germany, for the WHO, now suggest the infection can also spread simply by touching a contaminated doorknob or lift button.
However, it is still not known how much of the virus is needed for someone to become infected in these ways.
Dick Thompson from the WHO told the BBC he was confident the virus could be contained, without resorting to a vaccine.
"We believe it is definitely possible that we can eliminate the disease before it enters into a cycle and becomes endemic," he said.
There is as yet no cure for Sars, which first emerged in southern China last November.
But the WHO hopes the latest findings will help researchers develop better tests for the virus and possible treatments.
The WHO says Hong Kong, Singapore and Canada have now got the Sars outbreak under control.
But China is still struggling to contain the virus. Schools in the capital Beijing are to remain closed for another two weeks, and about 15,000 have been quarantined.