Medical researchers in Hong Kong are blaming different viruses for the deadly outbreak of atypical pneumonia that is spreading rapidly in the special administrative region of China.

One theory by a group of researchers from Hong Kong Medical University on Friday said the Serious Acute Respiratory Syndrome is caused by a new coronavirus transmitted through coughing, sneezing and indirect contact.

Coronaviruses are a family common in both humans and animals, usually causing sore throats and running noses in humans, professor Yuen Kwok-Yung from Hong Kong University medical team told the official Xinhua news agency.

Yuen said the new virus could live outside human bodies for about three hours. People could be at risk if they had touched contaminated objects and then rubbed their eyes or mouths. But, he adds, the virus could be easily killed by disinfectant.

On Thursday, another Hong Kong University research team claimed the virus belonged to the paramyxovirus, a different viral family.

"There are also other viruses identified which may be associated with the atypical pneumonia," said virologist Malik Peiris of the medical team.

A speedy diagnostic test will be available from Friday in Hong Kong's public hospitals to identify victims of atypical pneumonia, the Hong Kong University medical team said.

Hong kong, with 367 SARS patients, many of whom are in intensive care, and 10 deaths remains the most severely affected area, the World Health Organisation said.

Till Thursday, a cumulative total of 1,408 SARS cases and 53 deaths had been reported from 13 countries, the WHO said.