Unlucky combination: Dr Heinz Feldmann says an unlucky set of environmental and health events occurring simultaneously most probably contributed to the spread of SARS in Amoy Gardens in March.

An unlucky set of environmental and health events occurring simultaneously most probably contributed to the spread of SARS in Amoy Gardens in March, a World Health Organisation environmental health team has found.

In late March, an unusual cluster of severe acute respiratory syndrome cases occurred in Block E of Amoy Gardens Estate, and apartment units 7 and 8 were most affected. Hong Kong invited the WHO to send a team of environmental experts to assess what might have happened, following the Government's own review.

"We are impressed with the work that has been done here before," the WHO environmental health team leader, Dr Heinz Feldmann, said at a morning press briefing. "People here are knowledgeable and did a thorough job." The news from the WHO team is that the spread resulted from a combination of factors.

Presenting its initial finding to the Hong Kong Department of Health, he said his team has explored the risk factors involved in the possible environmental transmission of SARS in this housing estate and has concluded that a number of factors were probably responsible for the unusual virus spread.

Contributing factors

These events include:

* At the time of the outbreak, the floor drain traps in many apartments seemed to have dried out and did not contain water for long periods. Without this seal, the traps became an open connection to the soil pipe.

* Exhaust fans installed in some bathrooms were running with the door closed and droplets could have been drawn from the soil stack into the bathroom.

* The running exhaust fans could have also transported droplets present or generated in the bathroom into the light well, resulting in contaminated air encountering an open window and then entering into apartments even several floors away from the source.

* Flush water was shut down for 16 hours starting in the evening of March 21 to fix a break of a flush water pipe serving unit 8.This probably decreased the flow in the soil stack. Bucket flushing would have increased the generation of droplets in the bathroom.

Amoy Gardens' condition, management up to standard

The physical condition of the Amoy Gardens structure is generally good and meets international standards, Dr Feldmann said.

Building management is delivered by qualified personnel and existing plumbing systems meet the needs to contain waste within piping, as long as it is operated in the way it was designed to be used, he said.

The WHO team's exhaustive testing of Amoy Gardens found no genetic material or footprint of the SARS-related coronavirus in swabs taken from the affected apartments, the entrance between the units, the corridors, the roof, the ground floor and the sewer manholes.

"There was no evidence of live virus from the collected swabs," he said.

Lessons learned - preventing a future outbreak

Dr Feldmann noted that the steps to take to prevent a similar outbreak at Amoy Gardens in future are simple:

* People with U-type floor drains should make sure there is water in the drain at all times to form a seal.

* Keep bathroom windows closed.

* Many of the fans installed in Amoy Gardens' bathrooms "are far too powerful - they would serve an area 10 times the space". Because fans need air, consider putting ventilation slats in the bottom of the bathroom door.

Metropole outbreak due to 'hallway incident'

The WHO team also undertook investigations at the Metropole Hotel.

"The environmental team concluded at the Metropole there was an incident in the hallway of Floor 9 where the person with SARS contaminated people on the floor by some sort of close contact or secreted materials shed by the person," Dr Feldmann said.

The team found no problem with the sewer or ventilation systems. There was a horizontal spread on one floor, in one wing, and people were safe inside their rooms, he added. "The exposure seems to have happened in the hallway." 

He surmised that the index patient - the first person to have the disease that sparked the outbreak - may have vomited outside his room and cleaned it up without asking for help from hotel staff since there is no record of this.

The team also visited a block that experienced a mini outbreak at Tung Tau Estate. They have not yet finished their laboratory investigations. However, Dr Felmann said they did not find good evidence that the sewer system was involved.

The WHO expert team

The WHO environmental team, all from Health Canada, comprises:

* Dr Heinz Feldmann (team leader), an infectious diseases specialist/virologist, specialising in sampling, interpretation of data and epidemiology of communicable diseases;

* Immo Tilgner who has extensive expertise in mechanical building systems, including evaluation of ventilation and plumbing systems;

* Allen Grolla, specialising in technical sampling and analysis and molecular detection of viruses; and

* Dr Ramon Flick, a virologist with expertise in mechanical virology sampling and analysis and virus isolation from different samples.

The WHO will produce a full and final report in due course.

Government thanks WHO team for its report

At an afternoon press conference, Deputy Director of Health Dr Leung Pak-yin thanked the WHO for sending their experts here.

"By and large, the two reports are in compliance: the U-trap, lightwell and air circulation within it are very important factors," Dr Leung said. "Sewage pipe cleanliness, the treatment of the U-traps, the strength of the exhaust fans are significant factors that we have to pay attention to when we take care of our household safety."

The Government will examine the issues in the WHO team's report and make recommendations. Buildings in Hong Kong are designed up to standards - a point the report underlines.

"We're given more confidence, since our ideas are in compliance with international experts'," Dr Leung said. "We can reassure Amoy Garden residents about their living quarters."

Reports on other estates that have experienced mini outbreaks, including Tung Tau Estate and Koway Court, are still outstanding, he added.

"The most important thing is to give WHO and other countries in the world the confidence that Hong Kong can handle the SARS outbreak, and the number of new cases will remain low," Dr Leung said.