The incubation period, the amount of time between being infected and presenting one or more symptoms, had a range of an estimated 2 to 12 days, with an average of 4.6 days. The relatively long incubation period allowed the virus to be transmitted globally by asymptomatic air travelers without their knowing. 

Incubation Period of the SARS Epidemic, 2002-2003 

The infectious period is an important factor when considering the spread of an infectious agent. For SARS-CoV,  the efficiency of transmission to close contacts appears to be greatest from patients with overt clinical symptoms, which was usually during the second week following the onset of symptoms. 

Infectious Period of the SARS Epidemic, 2002-2003 

Case fatality rates (CFR) are used to describe the proportion of those infected that died from the disease compared to the total number of those who acquired the infection. In the case of SARS-CoV, the global average case fatality rate was estimated to be 15% by the WHO. However, it was also estimated that the CFR for patients younger than 60 years of age was 6.8%, while the CFR for patients older than 60 years was 55%. This shows that there is much variation in the mortality rate between age groups. 

Case Fatality Rates of the SARS Epidemic, 2002-2003 

- Incubation Period
- Infectious Period
- Case Fatality Rates

Saint Louis University

The epidemiological study and transmission dynamics of the 2002-2003 SARS-CoV epidemic can be classified into several key areas: the viral agent, environmental factors, superspreader events, specific transmission dynamics (such as incubation and infectious periods), and the chronological progression of the outbreak's first and second waves.

Epidemiology and Transmission Dynamics of SARS-CoV

Epidemiological investigations suggest that SARS probably emerged independently in several of Guangzhou’s satellite cities, circulating for at least two months before causing the outbreak in Guangzhou, the capital of Guangdong. The first wave was marked by the cases circulating around in Guangzhou’s satellite cities. The index case of SARS that fit the WHO definition was reported in Foshan on November 16, 2002. The second case was identified in a chef who reported having atypical pneumonia. This chef had regular contact with different types of live caged animals. He sought medical treatment in Heyuan, and similar cases to the Heyuan outbreak were found in Zhongshan. 

The First Wave of the SARS Epidemic, 2002-2003 

The second wave of SARS began when some complicated SARS cases from satellite cities were transferred to the major hospitals in Guangzhou for better medical care. The index case in Guangzhou was a seafood merchant who was admitted in late January of 2003. After staying in the hospital for 18 hours, more than 30 hospital staff were infected. Family members and relatives of the patient who had close personal contact with the patient had also become ill with the disease. This index case caused many secondary infections that further spread and gave rise to the outbreak in Guangzhou.

The Second Wave of the SARS Epidemic, 2002-2003 

Superspreader events resulted in several SARS epidemics outside of Guangdong. One of these events occurred in mid-February, when a doctor from Guangzhou traveled to Hong Kong, resulting in a major SARS outbreak within Hong Kong. He infected many other people during his stay at a hotel, also resulting in transmissions to other countries from this single case. International air travel allowed the disease to rapidly spread from Hong Kong to other parts of the world.

Superspreader Events of the SARS Epidemic, 2002-2003 

The environment of SARS included five regions that experienced moderate to severe epidemics: Hong Kong, mainland China (with the initial spread in Guangdong followed by a major outbreak in Beijing), Taiwan, Singapore, and Canada. SARS also spread to several other countries, although those countries had relatively low numbers of reported cases.

Environment of the SARS Epidemic, 2002-2003 

A previously novel coronavirus, SARS CoV was found to be the agent of SARS. There have been observations that led to speculations that the SARS coronavirus (SARS CoV) originated from a wild animal. Evidence from Guangdong suggests that most cases during the very early stages of the epidemic seem to have occurred in food handlers, those who kill, handle and sell animals and meat, as well as those who prepare and serve food.

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