SARS outbreak in H.K. housing estate not airborne: probe

Asian Economic News, April 21, 2003

HONG KONG, April 17 Kyodo

A probe into an outbreak of SARS in a Hong Kong private housing estate where some 320 residents have fallen ill concluded Thursday that the highly contagious disease was spread neither by an airborne or waterborne route, nor by cockroaches or rodents.

Human contact and environmental contamination were blamed for transmitting the disease quickly in Amoy Gardens where 41% of the cases came from its Block E building, which was sealed off and quarantined for 10 days after most of the tenants there were infected with severe acute respiratory syndrome (SARS).

''I would like to reassure the public that there is no evidence suggested the disease is transmitted by the waterborne route or by infected dust aerosols because we've done tests to show that,'' Secretary for Health, Welfare and Food Yeoh Eng-kiong said.

''And it is not so-called airborne as the public might see. It is clear from our epidemiological picture and laboratory results,'' Yeoh told a press conference.

The findings also showed that rodents had no signs of infection or disease, and pests are ''likely to be no more than mechanical carriers for the virus,'' he said.

It is probable SARS was spread from an index patient, or the first case of the outbreak at Amoy Gardens, to a relatively small group of residents within Block E and subsequently to the rest of the residents through the sewage system, person-to-person contact and the use of shared communal facilities such as elevators and staircases, he noted.

The outbreak at Amoy Gardens, which had reported 321 infections as of Tuesday, about a quarter of Hong Kong's cumulative total, had prompted concerns of the World Health Organization (WHO) over how SARS was transmitted in the city.

The WHO had issued an unprecedented alert asking international travelers to avoid Hong Kong and mainland China's Guangdong Province, the two areas hit hardest by the new strain of atypical pneumonia.

SARS killed four more people in Hong Kong, bringing the toll to 65 on Thursday. The number of infections in the territory now reached 1,297, with 29 new cases reported.

Worldwide, the disease has claimed at least 160 lives and some 3,300, mainly in Asia.

The Hong Kong government probe identified a 33-year-old man with chronic renal disease as the source of infection in Amoy Gardens.

The man came from China's Shenzhen special economic zone and visited his brother at his flat in Block E of the housing estate in the Kowloon Bay area last month. ''He was having diarrhea at that time and he used the toilet there,'' the report said.

The Shenzhen man developed SARS symptoms last month, and his brother, sister-in-law and two nurses who took care of him at hospital all later came down with the disease.

A survey of the patients from Amoy Gardens showed some 66% of them suffered diarrhea, in addition to common identified SARS symptoms of fever, chills and headaches, the report said.

Explaining the unusual mass infections, the government said it was apparent that a significant virus load was discharged in the sewerage in the 33-floor Block E and then transmitted through bathroom floor drains of flats that had dried-up, U-shaped water traps.

The virus could also be spread into flats with the use of bathroom exhaust fans, water vapor generated during a shower, and the moist conditions of the bathroom, the study suggested.

''Contaminated droplets could then have deposited virus on various surfaces, such as floor mats, towels, toiletries and other bathroom equipment,'' it noted, adding the droplets could also enter other units through open windows.

Leakage from the sewer vent pipe in Block E was another possible route of the disease transmission as it could have emitted droplets carrying contaminated sewage into the building's light well every time a toilet was flushed, it said.

A ''chimney effect'' of droplets rising inside the light well could have resulted under certain wind conditions, spreading the disease into the flats, it added.

The rapid spread of SARS in Amoy Gardens had sparked fears among the public that they might be infected at home.

But Yeoh said SARS cases found in other housing estates in the neighborhoods, including the Lower Ngau Tau Kok Estate and the Telford Gardens were due to people's movements and human contacts due to their proximity.

The health official rejected the suggestion that a housing estate, Koway Court, in the Chai Wan district where more than 10 infection cases were reported could be a repeat of an outbreak like that in Amoy Gardens.

To minimize the likelihood of similar outbreaks in future, the government has published guides to educate the public on the cleaning and disinfection of households, and the proper maintenance and repair of the drainage system and sanitary fittings.

The government said it will launch a territory-wide cleaning campaign over the weekend to improve environmental hygiene and pest control.