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Most dangerous community outbreak

Infected Death

Hong Kong 1755 300

Amoy Gardens 329 42

41% of the cases are from block E

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蘋果日報

SARS cases in Amoy Gardensrise drastically in just one week

Why?

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Amoy Gardens

Source: SARS Expert Committee

A majority of victims foundIn Wings 7 and 8: This isthe infection pattern of the virus!

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Mar 31 -The Hong Kong Department of Health imposed quarantine on Block E. The residents were later moved to an isolation camp, while the investigation team entered the buildings to find out the cause of the outbreak.

7Video watching: Still remember the “Isolation camp” ?

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• As shown in the video, all the Amoy Gardens Block E residents were moved to an isolation camp …

• You are the investigators trying to find out how the SARS virus is transmitted in Block E. Action now!

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Let’s recall the knowledge about transmission of diseases first …

The way that viruses spread depends on the type of virus.They can spread through:

• Carrier organisms – e.g. mosquitoes, fleas, rats, cockroaches• Air and water – by droplets or dust• Direct transfer of body fluids – e.g. sweat, blood saliva and semen• Surfaces on which body fluids have dried – door handles, lift buttons etc.

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Let’s start the investigation!

• In the video, the investigators said “Search every inch of the building for clues…”

Do you have any ideas in mind of what to search for?

• What samples could you collect?

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air

蘋果日報

Tips 1: List all the possibilities and collect samples. What’s next?

Sewage system

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Sewage system

蘋果日報蘋果日報

Water tank

Cockroach

Rat

air

Tips 2: Now we have known which samples contain virus, then?

13RatCockroach

Match the infection pattern?

Sewage system

蘋果日報

Tips 3: more than one sample contains virus, We have to figure out which samples match the infection pattern. But how?

Match the infection pattern?

Match the infection pattern?

Additional Information:Some Residents suffer from diarrhoea ( 腹瀉 )

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Step by step Analysis

Rats, Cockroaches, Sewage system

Which one?

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RatCockroach

Residents suffer diarrhoeaInfection patterns match!

Do not match the infection pattern

Sewage system

蘋果日報

Analysis result: Sewage system is the most possible cause for SARS to spread through the building!

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Let’s read the summary of WHO’s reportabout their investigation in Amoy Gardens

The sewage system of Amoy Gardensis presented in the picture

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“Super spreader” suffered from diarrhoea and passed the virus into the sewage system

WHO’s report on Amoy Gardens

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• Virus survives longer periods in sewage

• U-trap of floor drains dried up providing a pathway for the droplets containing Virus into the bathroom

• Exhaust fan on, door closed• creates low air pressure in bathroom

“Super spreader” suffered from diarrhoea and passed the virus into the sewage system

WHO’s report on Amoy Gardens

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• The exhaust fan sucks contaminated droplets to the light well (天井 )

• The viruses are carried to higher levels by the warm humid air

“Super spreader” suffered from diarrhoea and passed the virus into the sewage system

• Virus survives longer periods in sewage

• U-trap of floor drains dried up providing a pathway for the droplets containing Virus into the bathroom

• Exhaust fan on, door closed• causes low pressure in bathroom

WHO’s report on Amoy Gardens

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• So….. What can you do to reduce the risk of spreading or contacting virus?

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• Cover your mouth or nose when you sneeze or cough.

• Wash your hands with soap frequently, especially after going to the bathroom or preparing food. Dry with hot air or paper towel

• Avoid contact with the body fluids of others.

Examples

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After the investigation, you should be aware that careful analysis and logical arguments are very important for scientific investigation.