Five other elderly patients admitted earlier from the same home for the aged remain in hospital. All six patients were in stable condition while four others had already tested negative for the coronavirus, she said.

Meanwhile, tests were continuing on another three female elderly patients, aged between 81 and 86, from an old-age home in Hunghom. They were recently admitted to the hospital with chest infections while one of them also had a fever.

And Caritas Medical Centre said five of the 10 elderly patients recently admitted with similar symptoms had recovered and were sent home, while the other five were being closely monitored.

These cases are the latest in a string of Sars alerts during the past two weeks in which the first stage of a new three-tier warning system for the disease has been raised amid heightened fears the deadly virus could return as the weather turns cooler. The spokeswoman said the 'green' alert was still in effect at both hospitals, and visits to the wards concerned were not allowed.

Meanwhile, the Hospital Authority yesterday appealed to recovered Sars patients to take part in a blood donation programme to assist research into hyperimmune globulin.

An authority spokesman said hyperimmune globulin was proposed as a means of preventing infection after unprotected exposure to the Sars virus, such as that experienced by healthcare workers.

The spokesman said each recovered patient could donate 500 centilitres of blood plasma in each donation, and there were 1,000 recovered Sars patients aged between 18 and 55 who were suitable donors.