SARS and the Warning Signs

In 2003, a new coronavirus emerged. We should have been ready for its successor.

SARS (Severe Acute Respiratory Syndrome) killed about 800 people worldwide before being contained. It demonstrated exactly how a coronavirus could spread through the air—but many of these lessons were forgotten or ignored when COVID-19 emerged 17 years later.

Date	Event
Nov 2002	First cases appear in Guangdong Province, China
Feb 2003	Dr. Liu Jianlun, infected in Guangzhou, stays at Hong Kong hotel; spreads virus to at least 16 guests
Mar 2003	Cases appear in Vietnam, Singapore, Canada; WHO issues global alert
Apr 2003	Amoy Gardens outbreak in Hong Kong: 329 cases in one apartment building
Jul 2003	WHO declares SARS contained; last human case

Definition: An event where one infected person transmits the virus to many others—far more than typical.

Key SARS Superspreading Events

Event	Setting	Infections	What Happened
Hotel Metropole	Hong Kong hotel	16+	One sick doctor infected guests on same floor; they spread virus to multiple countries
Amoy Gardens	Apartment building	329	Virus spread through building's plumbing/ventilation system
Hospital wards	Multiple hospitals	Hundreds	Healthcare workers infected while using insufficient protection

Pattern: Most SARS patients infected few or no others. But a small percentage of patients—in the right (or wrong) conditions—infected dozens.

This outbreak revealed that SARS could spread through the air in unexpected ways.

What Happened

• One patient with diarrhea visited relatives in Building E
• Within days, 329 residents were infected—mostly in Building E
• Cases were concentrated in apartments stacked vertically above each other
• Many infected residents had never met the original patient

The Investigation Found

• Virus particles were aerosolized from contaminated sewage
• A faulty bathroom exhaust system spread virus-laden air between apartments
• Dried-out U-traps in floor drains allowed sewer gases to enter apartments
• Prevailing winds carried particles to other buildings

Conclusion: SARS could spread through airborne routes, not just close-range droplets.

Successful Strategies

• Early detection: Aggressive testing and contact tracing
• Isolation: Infected patients were isolated quickly
• Quarantine: Exposed contacts were monitored
• Healthcare infection control: Hospitals improved protocols
• Travel restrictions: Affected areas were avoided
• International cooperation: WHO coordinated global response

Key factor: SARS patients were mainly contagious when symptomatic, making it easier to identify and isolate them before they spread the virus.

Factor	SARS (2003)	COVID-19 (2020)
Spread before symptoms	Rare	Common (40-50% of transmission)
Case fatality rate	~10%	~1% (varies)
Mild cases	Rare	Very common
Detectability	Easy to find sick people	Many spreaders didn't know they were infected
Containment	Possible with isolation	Much harder due to pre/asymptomatic spread

Paradox: COVID-19's lower fatality rate made it more dangerous at a population level because infected people felt well enough to spread it widely.

1. Why do you think the lessons from SARS about airborne transmission weren't widely applied?
2. How did the Amoy Gardens outbreak change our understanding of how respiratory diseases can spread?
3. If SARS had not been contained, how might history have been different?
4. What systems or preparations could have been put in place between 2003 and 2020 to better handle the next pandemic?

Analyze the Amoy Gardens Outbreak

Using the information provided, create a diagram showing:

1. How the virus entered the building
2. How it spread between apartments
3. What building features contributed to spread
4. What interventions could have prevented spread

Questions to Consider

• Why were apartments stacked vertically most affected?
• What role did the ventilation system play?
• How could building design be improved to prevent similar outbreaks?
• What would you recommend for apartment building safety today?