The severe acute respiratory syndrome-coronavirus has been under rapid mutation and there is more than one form of the virus in Hong Kong.

These are the conclusions of the Chinese University's research on the genetic fingerprint of the virus from 11 patients since the outbreak in March.

The university's Professor Dennis Lo said analysis revealed that the genetic signature of the virus could change even between its transmission from one wave of infection to the next. The evolution could take place in as little as two weeks.

The study also found that genetic signatures of some patients are different from the one involved in the Prince of Wales Hospital cluster.

"This indicates that more than one type of SARS-coronarvirus is present," he said, adding that the findings will help identify the origin of SARS.

The university's Professor Sydney Chung said SARS was an extremely infectious virus.

Asked why medical staff are more prone to contracting the disease, he said hospitals are loaded with viruses due to the large number of patients. Staff also have to perform high-risk duties like intubation and extraction of mucus which might lead to transmission of the virus.

He stressed that sufficient precautionary measures should be taken to avoid infection.