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Transcript of SHWF on the findings of an investigation of severe acute respiratory syndrome outbreak at Amoy Gardens

Following is the transcript of remarks by the Secretary for Health, Welfare and Food, Dr Yeoh Eng-kiong, at the press conference on the findings of the investigation into the outbreak of severe acute respiratory syndrome (SARS) at Amoy Gardens today (April 17):

Secretary for Health, Welfare and Food, Dr. Yeoh: In the past few weeks, we have put together a multi-disciplinary team of eight government departments to conduct a very detailed and thorough investigation into the outbreak of SARS at Amoy Gardens. I am particularly grateful to the Secretary for the Environment, Transport and Works, Dr Sarah Liao, who really offered her assistance and expertise on the environmental aspects of the investigation, and certainly to the other Government departments taking part. The investigation is all-embracive, covering epidemiological, environmental, public hygiene, building designs and utilities aspects. So, it is a very detailed and thorough investigation. We have completed our investigations and we are presenting our major findings today. However, before we go into the details of the findings, I think it is important for the public to understand that any investigation of this nature will always be conducted under some limitations, not least because we have an incomplete understanding of the disease and the need to minimise inconvenience and distress to the affected residents. Nonetheless, we are of the view that we have done all that is possible and looked into all the possible and probable causes of this outbreak at Amoy Gardens, and the findings help us identify effective actions to tackle the situation.

I shall now turn to the major findings, beginning with the epidemiological investigation. First, if you remember we have said that the index patient, the person that we believe was the source of the infection, was a 33-year-old man who lived in Shenzhen and visited his brother in Amoy Gardens regularly. This individual had chronic renal disease and was being treated at Prince of Wales Hospital. He developed symptoms of SARS on March 14, and on both March 14 and March 19, he visited his brother who is a resident of Block E of Amoy Gardens. He had diarrhoea at the time and had used the bathroom. His brother and sister-in-law and two nurses who attended to him at the Prince of Wales Hospital subsequently also developed SARS. As of the 15th of April we now have a total of 321 individuals affected by SARS who lived in Amoy Gardens. There is a very obvious concentration of individuals in Block E who were affected, accounting for 41per cent of these 321 cases. Other blocks in Amoy Gardens - if you remembered Block E has 33 floors with eight apartment units on each floor. Units 7 and 8 had the highest rates of infection. Seventy-three per cent of the units in Unit 8 had individuals who were infected by SARS, so the attack rate was 78 per cent. Unit 7 had 42 per cent of the units affected, so these were very high attack rates in Units 7 and 8 of Block E. So Block E has 8 units and there was a very high attack rate in both units 7 and 8. In terms of onset dates, the outbreak reached its peak on March 24 and declined steadily thereafter. Cases in Block E appeared earlier, generally about three days earlier, and in the outbreak, it showed a point-source type distribution - one event occurred and led to the contamination and all the infections followed that event. Cases in other blocks appeared three days later and were more evenly spread out in time. So when you look at the onset of illness, we believe that the patient was the initial source of infection. He infected a number of residents in Block E and then the rest of the residents in Block E. The other blocks in Amoy Gardens were affected about three days later. So when we look at the onset dates, there is a very clear time lag between the onset of infections in Block E and the onset of infections in the other blocks - a three-day time lag.

The Department of Health had also conducted a questionnaire to look at the common symptoms of SARS in this outbreak, and a very notable feature is that 66 per cent of all the patients who came down with SARS had diarrhoea. It also showed that four per cent had contacts with SARS patients and eight per cent had visited the Mainland during the period. So the very notable feature of this outbreak is that 66 per cent or two-thirds of the patients had diarrhoea.

I shall now turn to the environmental investigations. What we see is a very important and integral part of our overall investigation, and we need to explore and examine all possible and probable causes of this outbreak. I would like to give a summary of our findings. First, you can see that with each block, there are eight vertical soil stacks, each collecting effluent from the same units of all floors. The soil stack is connected with the water closets, the basins, the bathtubs and the bathroom floor drains. Each of these sanitary fixtures is fitted with a U-shape water trap, the U-trap. This U-trap prevents foul smells and insects in the soil stack from entering the bathroom. So, you have a U-shape water trap that is intended to be filled because once you fill it with water you don't get the reflux of the smells and the sewers back into the households. For this preventive measure to function properly, the water traps must be sufficiently filled with water. So, it's a very simple device. Interviews with Amoy Gardens residents revealed frequent complaints about foul smells in the bathrooms, which suggested that the U-trap arrangement might not be functioning properly in some units. As the water closets, the bath tubs and the basins were frequently used, their U-traps should be charged with water and should have been functioning properly. However, as most households have the habit of cleaning the bathroom floor by mopping instead of flushing with water, the U-traps connected to most floor drains were likely to be dry and were not functioning properly. In the test carried out by Dr Liao's team in one of the units in Block E, reflux of air from the soil stack into the bathroom to the floor drain was demonstrated when the exhaust fan in the bathroom was switched on. It can therefore be postulated that the reflux could have contained droplets of contaminated sewage present in the soil stack. The contaminated droplets were then dispersed into the bathroom. Dr Liao's team also conducted a tracer dye test on the sewage pipe, but no leakage was confirmed. However, by using an oil droplet test a crack in the sewer vent pipe at the fourth floor level was located. The vent pipe is connected to the branch soil pipe, to equalise the air pressure between the main soil stack and the branch soil stack. In theory, any leakage in the sewage system is important as it could allow droplets carrying contaminated sewage to be ejected into the lightwell. However, the amount of virus ejected and the velocity of the emission cannot be quantified. So there are these possible mechanisms where the sewage could really go into the flats through the mechanisms I've described.

We also saw signs of cockroach infestation in Amoy Gardens in particular around the carpark, food premises and drain openings. Rodent activities were also detected around refuse collection chambers, the carpark and food premises. So these were evidence of pest infestation. So this is part of the environmental investigation.

The third part is that we did laboratory investigations. A collection of air samples, water samples, environmental swabs and animal swabs droppings sera were taken in Amoy Gardens to identify the extent of the environmental contamination by the causative agent. No abnormalities were detected in the air and water samples. One environmental swab collected from the inner room of a toilet in Block E where a SARS patient is a resident was positive for the virus that we know causes SARS, the coronavirus. So we were able to detect in the toilet of one of the resident's flats, the presence of coronavirus. Coronavirus was also detected in the pest droppings and in some instances on the surfaces of the cockroaches. As the rodents showed no sign of infection or disease, the findings only point to environmental contamination at Amoy Gardens and pests are likely to be no more than mechanical carriers for the virus in this outbreak. So, because the rodents were not infected and there was no sign of disease, the finding demonstrates that all these findings are part and partial of the environmental contamination because it could have affected anyone who had been in physical contact with some of these environmental samplings. So these were just passive mechanical carriers.

Secretary for Health, Welfare and Food: The rodents were not infected and there was no sign of disease. So all these findings are part and partial of environmental contamination, because it could have infected anyone who was in physical contact with some of these environmental samplings. So they were just passive, mechanical carriers.

I would like now to go to the possible explanation for the outbreak. I would like to reassure the public that there is no evidence to suggest that the disease is transmitted by the waterborne route, or by infected dust aerosols because we have done tests to show that. And it is not, so-called, airborne, as the public might perceive. This is clear from our epidemiological picture and the laboratory results. Given the unique distribution pattern of infected Block E residents and taking into account the contact with SARS patients and the large number of patients reported with diarrhoea symptoms, environmental factors played a major role in this outbreak. So you see that the very unique pattern of distribution and the large number of patients affected with diarrhoea symptoms. Environmental factor must be a major part of this outbreak. The studies also show that many patients with SARS, excrete coronavirus in stool. So, this is based on a lot of studies now that we know that patients with SARS not only with its virus present in the droplets and respiratory secretions and is also present in many body fluids and in particular present in the stools of patients with SARS. And where the SARS could survive for periods, the define periods, we cannot have any knowledge but certainly the studies initially done in the University of Hong Kong demonstrates the SARS virus can survive in faecal samples. Many patients in the Amoy Gardens outbreak had diarrhoea contributing to a significant virus load being discharged into the sewer system in Block E. So it is not just one patient because the patient, in fact, a number of individuals in Block E who also had diarrhoea. So, it led to quite a large amount of virus being present in sewage system.

It is probable that the index patient initially infected a relatively small group of residents within Block E and subsequently the rest of the residents within that block through the sewerage system, person-to-person contact and the use of shared community facilities such as lifts and staircases. These residents subsequently transmitted the disease to others, both within and outside Block E through person-to-person contact and environmental contamination. So we have a sequence of events. The patient initially infecting a small number of individuals in Block E, who then infected the rest of the residents and the rest of the community in Amoy Gardens. And we believe the main source of infection is the excreta in the sewerage system.

The bathroom floor drains, the dried-up U-traps provide a pathway through which residents came into contact with droplets containing virus from the contaminated sewage. So the U-shape prevents the reflux if it's not filled, then you can get these droplets going back into the flats. When the bathroom was in use, with the door closed and the exhaust fan switched on, there could be negative pressure to extract contaminated droplets into the bathroom. So, you can see that if you have exhaust fans which withdraw air from within the pipes, you then create a system where the droplets would be facilitated to go into the bathrooms. Contaminated droplets could then have been deposited on various surfaces such as floor mats, towels, toiletries and other bathroom equipment. So, you have this effect of drawing droplets into the bathroom. Water vapour generated in the shower and the moist conditions of the bathroom could also have facilitated the formation of water droplets. The chance of exposure was increased given that the bathrooms in the units in Amoy Gardens were generally very small. They are only about 3.5 square metres.

We believe there could also be secondary cases of transmission through close contacts with cases. So there is a whole series of methods of infection. One is through the sewage -- through droplets, the second is through person-to-person contacts, and the third is through environmental contamination. So there were three routes of infection giving rise to this outbreak in Amoy Gardens.

Just to summarise the actions the Government took to tackle the situation. We conducted disinfection and thorough cleansing with the co-operation of the owners and the residents. Particular attention was paid to the sinks, bathrooms, bathtubs, wash basins, toilet bowls, floor drains in the bathrooms and kitchens and the water storage tanks were cleansed. Subsequent tests for E. Coli showed that disinfection of the drain pipes was effective. So we took a whole series of actions. We insured that these were sterilised and cleaned, met our standards before the residents were allowed back in.

The Food and Environmental Hygiene Department gave advice to residents on how to disinfect their flats as a precautionary measure, teaching them all the things they should do. The residents were also advised to keep sufficient water in the U-traps of drainage outlets to ensure proper functioning. Remember the U-traps, we believe, are a very key part of the whole process and of course this is something that we also want you to inform the public of because these U-traps are in all our flats and they should be filled with water.

To minimise the likelihood of similar outbreaks in future, we have produced a guide to educate the public on cleansing and disinfection of households, including bathroom cleansing, ensuring the proper functioning of the water seal and U-traps. So this is what we talked about U-traps and that is why they are so important because the U-traps prevent the reflux and also prevent any cockroaches from climbing the drainage back into the flat. If the U-traps are filled, then the sewage does not go back into the flats and the cockroaches also do not go back into the flats. So it is very simple device.

Improvements to environmental hygiene will be made and pest control will be stepped up on a territory-wide basis.

The management company is carrying out a comprehensive inspection of the drainage system of the blocks within the development. We have also published a set of guidelines to draw the attention of the public to proper maintenance and repair of the drainage system and sanitary fixtures. The guidelines are available from the Buildings Department website and have been distributed to all management companies and owners' corporations.
The buildings management authorities of buildings where confirmed SARS patients reside have been notified of the infections and are required to take proper disinfection measures. Because of the knowledge now on how infection spread within a block of households, now that once we have a case of SARS notified, we then inform building management of what they should do to prevent any possible transmission within that building. That's why every time that we are isolating an individual, we advise the building management and the names of the buildings are on the web. So people know what action has been taken and who should take appropriate action.

The Food and Environmental Hygiene Department (FEHD) will inspect buildings to see they meet required standards. Major cleansing and disinfection procedures were also conducted in Lower Ngau Tau Kok Estate, Telford Gardens and the surrounding areas, by building management working with the FEHD. We also want to emphasize that the infections that we see in Lower Ngau Tau Kok, Telford Gardens and Lee Kee Building were all related to the Amoy Gardens outbreak because of their geographical vicinity and there were a lot of people movements between Amoy Gardens and these estates. In our investigations, we found that many residents in Amoy Gardens had relatives in some of the other estates, particularly in Lower Ngau Tau Kok, because some of the families and some of the individuals in Amoy Gardens, when there was an outbreak of the disease, in fact moved back to Lower Ngau Tau Kok. So we believe that the infections in these surrounding areas were due to people movements and the environmental contamination in Amoy Gardens where some of the residents in adjoining districts visited as well. So when you look at the whole control of Amoy Gardens, the rest of Amoy Gardens and the peripheral districts was an event that occurred subsequent to the outbreak in Block E.

(Chinese portion)

I also want to just highlight that in fact there was some concern about Koway Court that the same case was happening. I just want to say that this morning in fact the Chief Executive and I went to Koway Court to look into the investigations that were going on there. And obviously the CE was very concerned that we do not have another outbreak similar to that of Amoy Gardens. We will assure him that it would not occur because the environment ecology is very different. We had looked at the orientation and the number of people affected. Obviously the number affected is fortunately very small. This time we have learned from the lesson from Amoy Gardens. We took very quick action. We took very quick action because the team from Department of Health and the Food, Environment and Hygiene Department and all the other government departments worked very closely and very well to really make sure that the infections did not spread in that community. We did not find any evidence of sewage leakage or any of the problems that we saw in the Amoy Gardens. So the situation is different. If we now see two cases in one building, we want to make sure that there could not be any potential outbreak in any building.

(Please also refer to the Chinese portion)


End/Thursday, April 17, 2003
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