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(18/04/03) |
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Amoy Gardens outbreak linked to sewage leak
This is among the conclusions of a government investigation into the outbreak at the estate in which at least 321 patients were infected - more than 40 per cent of them in Block E. The two-week study also found rodent(齧齒目動物的) droppings(鳥獸的糞便) and cockroaches were passive carriers of the coronavirus that was believed to have caused the global outbreak of potentially fatal Severe Acute Respiratory Syndrome (SARS). Announcing the findings yesterday, Secretary for Health, Welfare and Food Yeoh Eng-kiong said the U-shaped floor traps should have contained water to stop smells or contamination from the main sewage drain pipes into which they fed. But many were found to be dry, allowing droplets containing the virus, which could be faeces-borne, to enter the bathrooms, possibly sucked in by the negative pressure of extractor fans. A ``large, visible crack'' in a sewer vent pipe on the fourth floor is also thought to have spread contaminated(弄髒;污染) droplets into the building's light well(天井),, where they were spread to the flats by what was termed a ``chimney(煙囪) effect''. It said the soil stack - the main vertical disposal pipe - was connected to the toilets, basins, bathtubs and the bathroom floor drains, each with a U-shaped water trap. ``As most households clean their bathrooms floor by mopping(用拖把擦洗地板) instead of flushing(用水沖洗) with water, the U-traps are dry. Tests carried out in one unit found a reflux of air from the soil stack into the bathroom through the floor drain when the bathroom exhaust fan was switched on,'' the report said. The dysfunctional U-shaped traps were likely to have been ``a major way of transmission'' in Block E, Yeoh said, noting that an infected patient had ``discharged a significant virus load'' into the sewage system there. Infected residents had further spread the disease through person-to-person contact, while rodents and cockroaches might have helped to carry the viruses around, he said. Although the probe revealed that the ``index'' patient - a 33-year-old with chronic kidney disease who visited his brother at Amoy Gardens last month - lived in Shenzhen, Yeoh said there was no evidence the virus originated from the mainland. Yeoh also ruled out(排除) the possibility that coronavirus could be airborne. ``Airborne diseases are highly infectious. If viral pneumonia was airborne, the number of patients would come in waves and it would not be as little as around 300 in Amoy Gardens alone. It would continue to grow by thousands,'' he said. Yeoh said the spillover(外流人口) from Amoy Gardens infected 65 other residents in nearby housing estates such as Telford Gardens, Lee Kee Building and Lower Ngau Tau Kok Estate. Nine of the Amoy Gardens patients have died. Yeoh said the virus was found to have a three-hour lifespan in open areas but could live up to 24 hours in faeces. The report revealed that the inner rim of a toilet in a flat of Block E tested positive for coronavirus. An oil droplet test had shown that droplets could rise in the 1.5-metre wide light well. ``Contaminated droplets ejected into the light well through a leaked pipe could travel upwards and enter the windows of upper floor flats,'' Secretary for the Environment, Transport and Works Sarah Liao said. ``But it's not airborne as the virus will die without being carried by droplets, and airborne viruses need no carrier.'' Director of Buildings Marco Wu said 1.5 metres was the legal width for a light well. Wu suggested pouring one to two litres of water into the floor drain once a week to keep the U-traps filled with enough water to block any reflux(逆流;退潮) of air or insects that might carry a virus. Residents who returned home last week after 10 days in quarantine camps had mixed reactions. ``If the sewage pipe is found to be the cause of the outbreak, it must be replaced. Filling the U-traps with water is not a lasting solution. We are willing to foot(【口】支付(帳單或費用) the bill,'' a Block E resident, who identified himself only as Lee, said. Another, identifying himself only as Tsang, said: ``I don't quite believe the report. I have been cleaning the toilet of my home all along. Should I quit my job to spend the whole day cleaning?'' The Hong Kong Institute of Surveyors said the investigation showed the incident at Amoy Gardens was caused by the misuse and mismanagement of the sewage pipes. ``If the management company did not have a proposal for the regular inspection and maintenance [of these sewage pipes], a problem would exist,'' president Kenneth Chan said. He described the Buildings Department's reporting mechanism, under which it acted on complaints, as ``only a passive practice''. He said responsible management companies should conduct regular inspection and maintenance of pipes. Chan suggested tenants could use a piece of cloth or adhesive(黏著的;有黏性的) tape(膠布) to block the floor drain hole. Yeoh, who said Amoy Gardens outbreak had been dying down(逐漸消失) in the past days, explained why Block E residents were evacuated(撤空,撤離) the second day being placed under home quarantine. ``We only started to suspect the sewage system as a way of transmission on the second day of the isolation order, and that's when we ordered the residents to stay at holiday camps.''
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