The Secretary for Health, Welfare & Food says the World Health Organisation in lifting its travel advisory will judge Hong Kong's case on its own merits.

Dr Yeoh Eng-kiong told legislators today the WHO's three conditions for lifting Hong Kong's travel advisory are only general criteria.

He said their final decision will mainly be determined by the number of daily cases, while the second major consideration will be whether the disease control measures are effective.

Dr Yeoh said he felt the WHO will be flexible in its judgement.

Healthcare workers not outbreak source

Meanwhile, Dr Yeoh said SARS has been spread locally through three major sources: the Prince of Wales Hospital, Amoy Gardens and sewerage from infectious housing blocks.

He said the hospital cases were first spread from a SARS patient to many healthcare workers and visitors. Healthcare workers then spread the virus to their families, and these cases represented only a small fraction of the total cases.

In Amoy Gardens, various environmental factors, including the drainage and piping systems, particularly U-shaped water traps, had contributed to another spread in the community.

The U-shaped water trap may have also led to small outbreaks at Koway Court in Chai Wan and Hing Tung House in Tung Tau Estate.

It is hoped that announcing the list of buildings with SARS patients will raise the awareness of building management companies of the environmental hygiene of their blocks.

Actual cases should be less

Dr Yeoh said the source of spread in about 20% of SARS cases still could not be ascertained. The antibodies of the concerned patients will be examined to find the causes.

The actual number of SARS cases should be lower than announced, he said. The daily average number of cases in the past six weeks has dropped substantially: from 49 on March 25-31 to 11 on April 29-May 5.

Since mid-April, the number of recovered and discharged patients has been steadily increasing from a cumulative total of 84 on April 1 to 958 yesterday.

The number of patients under treatment in hospitals (including those who are undergoing convalescence) has therefore been dropping from the peak of 960 on April 17 to 495 yesterday.