HIST4702 (2022-23) Digital History Project: SARS in Asia
3D Modelling: Transmission of SARS in Amoy Garden, Hong Kong
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Description
In late March 2003, a large number of Amoy Gardens residents contracted severe acute respiratory syndrome (SARS). The first case of the epidemic was a 33-year-old man who lived in Shenzhen and frequently visited his brother at Amoy Gardens. On March 14, he used the toilet due to diarrhoea while visiting his younger brother at Amoy Block E. Subsequently, his younger brother, his sister-in-law and the medical staff who attended them all contracted SARS; Two weeks later, SARS broke out in Amoy Gardens. On April 15, there were 321 SARS cases in Amoy Gardens. The infected cases were significantly concentrated in block E, accounting for 41% of the cumulative total. The second most infected cases were recorded in Block C (15%), the third were in Block B (13%) and the fourth were in block D (13%). The remaining cases (18%) were scattered among the other 11 blocks. The number of residents of Block E of Amoy affected by SARS was 107, most of whom lived in the vertical units 7 and 8 of Block E.
There are 19 blocks in Amoy Gardens. Like the other buildings in Amoy Gardens, Block E is 33 storeys high with eight flats on each floor. Each building has eight vertical sewage pipes to collect sewage. This sewage pipe is connected to the water toilet, washbasin, bathtub and bathroom floor outfall, each of which is equipped with a U-shaped water concentrator. Each building in Amoy Gardens has eight vertical sewers to collect sewage from all buildings of the same floor code. This sewage pipe is connected to the floor drain of the water toilet, wash basin, bathtub and bath room. Each of these sanitary installations is equipped with a U-shaped water condenser to prevent foul smell from sewage pipes and insects from entering the toilet. The condenser must have enough water storage in order to play its role of air isolation. The prevalence of complaints relating to odors in toilets suggests that the U-shaped water concentrators connected to some units may not be functioning as intended.
Argument
As we have not constructed the model under rigorous scientific demonstration and deduction, there is no way for us to give an argument on how SARS broke out in Amoy Garden. We instead are trying to represent the findings in government reports and other studies through 3D-modelling. There are the findings we would like to share from the investigation on the outbreak of SARS we based in constructing the models. The bathroom windows, exhaust fans, plumbing, and laundry racks are all positioned in Block E’s reentrant areas (as is typical in Hong Kong housing blocks). Water vapour from bathroom exhaust, clothes drying, and broken sewer pipes can follow the air flow into neighbouring apartments. The airborne particulate matter released by the nearby high-rise construction project has the ability to spread from one flat to the next. Residents came into contact with tiny droplets harbouring viruses from the tainted sewage via the bathroom floor drains with dried-up U-traps. These drops entered the bathroom floor drain due to the negative pressure created by exhaust fans when the door was closed. Water vapour produced during a shower, as well as the moist conditions of the bathroom, may have aided in the creation of water droplets. Contaminated droplets may have eventually deposited the virus on a variety of surfaces, including floor mats, towels, toiletries, and other bathroom equipment. Wind-driven vertical flow exists in the reentrant space, which is influenced primarily by the geometry of the reentrant and its orientation to the prevailing wind. The air in the reentrant region between Block E’s Units seven and eight moves slowly. The quick horizontal flow across the reentrant’s mouth, through the short gap between Blocks E and F, creates a “air curtain” effect, which obstructs ventilation of the reentrant interior.
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