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SARS-CoV (Severe Acute Respiratory Syndrome)

Public Health Agency of Canada CORONAVIRUS HOTLINE 1-833-784-4397

There are currently no cases of Severe Acute Respiratory Syndrome (SARS-CoV) anywhere in the world. The following information has been retained for historical purposes. Please note that some links may no longer be working.

For information on Coronavirus (COVID-19) SARS-CoV-2. Click here


On April 16, 2003 researchers around the world established a hitherto unknown virus as the cause of SARS. The new coronavirus has been named by WHO and member laboratories as "SARS-CoV Virus" [image of virus]. Thirteen laboratories worked on meeting Koch's postulates, necessary to prove disease causation. Koch's postulates stipulate that to be the causal agent, a pathogen must meet four conditions: it must be found in all cases of the disease, it must be isolated from the host and grown in pure culture, it must reproduce the original disease when introduced into a susceptible host (in this case, monkeys), and it must be found in the experimental host so infected. Credit for the coronavirus findings, which definitively pinpoints the cause of SARS, is attributed to the 13 laboratories, working in conjunction with WHO. This discovery now enables scientists to concentrate on developing diagnoses kits, treatments and, eventually, the possibility of a vaccine. [ref: WHO, 16 April 2003 ]

There is some evidence that the SARS virus originated in animals and crossed into humans, and work is continuing to confirm this. Animal testing has shown that co-infection with other viruses (e.g. metapneumovirus) does not affect the virulence of the SARS virus or act in a symbiotic fashion with it, as earlier suspected. Many animal species appear to be able to carry the SARS virus. [WHO] In a recent seroprevalence study carried out in Guangdong Province in China (the "birthplace" of SARS), "serologic evidence suggests that asymptomatic infection with SARS-CoV or an antigenically related virus occurred in Guangdong Province. Seroprevalence of IgG antibody to SARS-CoV was substantially higher among traders of live animals than among persons in control groups, consistent with the hypothesis that SARS-CoV crossed the species barrier from animals to humans. The results are consistent with preliminary determinations of a joint research team from China's Ministry of Agriculture and Guangdong Province, which found that sequences of coronavirus detected by polymerase chain reaction in bats, monkeys, masked palm civets, and snakes were identical to or similar to those of human SARS-CoV isolates. In addition, a joint study by Shenzhen CDC and Hong Kong University determined that the sequence of coronavirus isolated from masked palm civets is 99 percent identical to human SARS-CoV. These determinations appear consistent with the hypothesis that an animal reservoir exists for SARS-CoV or an antigenically related virus; however, the findings are not sufficient to identify either the natural reservoir for SARS-CoV or the animal(s) responsible for crossover to humans. This report provides indirect support for the hypothesis that SARS-CoV might have originated from an animal source and identifies multiple animals for further study".  [ref: ProMed Oct. 16, 2003].



Symptoms of the illness, in order of observed frequency, include high fever, non-productive cough, shortness of breath, malaise, diarrhea, chest pain, headache, sore throat, myalgias and vomiting. Lymphopenia, elevated LDH levels, elevated AST levels and elevated creatine phosphokinase levels have also been reported [ref: Health Canada]. About 10% of patients decline around day 7 and require mechanical assistance to breathe. Symptoms appear to be worse in the second week of illness and onwards.


The primary mode of transmission of the SARS virus is direct mucous membrane (eyes, nose, and mouth) contact with infectious respiratory droplets and/or through exposure to fomites (objects contaminated with infected material). SARS does not appear to be airborne. Most of the data have been consistent with transmission through large droplets or body fluids. Aerosol transmission cannot be totally discounted, but if it occurs it is uncommon. If the causative organism had been readily transmissible by aerosol, many more cases would have been expected, especially in the countries where transmission has slowed or never started.  Aerosolizing procedures in hospitals (such as nebulization), and other events that promote aerosolization of infectious respiratory droplets or other potentially infectious materials (such as faeces or urine) in hospitals or other settings, may amplify transmission.

The incubation period ranges from 2 to 10 days, with a mean of 4-6 days and a median of 4-5 days. The minimum reported incubation period was 1 day and the maximum was 14 days. It is still unclear whether the route of transmission influences the incubation period.

Transmission efficiency appears to have been greatest from severely ill patients or those experiencing rapid clinical deterioration, usually during the second week of illness. Data from Singapore showed that few secondary cases occured when symptomatic cases were isolated within 5 days of illness onset. Viral shedding of the SARS virus was relatively low during the initial phase of illness, and peaked at about day 10 of illness in respiratory specimens. Virus shedding in stool began later than in respiratory secretions, with most samples showing positive PCR by day 12-14 and then declining. This made testing difficult in the early stages of the disease. Some persons appeared to be "super-shedders", with very high viral loads that resulted in transmission. There is presently no evidence to suggest that disease transmission occurs prior to the onset of symptoms in a suspected or probable case of SARS [Health Canada].

In Hong Kong there were some patterns of infection that are most easily explained by environmental transmission. Evidence suggests that the virus survives in faeces and urine at room temperature for at least 1-2 days, and appears to be more stable in stool from patients with diarrhoea (up to 4 days), possibly related to the increased pH. The SARS virus survives freezing. Heat at 56°C for 15 minutes kills the virus, as does exposure to many common disinfectants and fixatives [WHO].

The index case in Ontario was an individual who travelled to Hong Kong and stayed at the Metropole Hotel, where a cluster of SARS cases was subsequently identified [ref: MMWR Vol 52, No. 12, March 28, 2003]. Two clusters of cases in Toronto represented community transmission resulting from late diagnosis of cases within a small religious group and persons who attended a funeral.

The experience in Canada illustrates that highly developed countries can be vulnerable to transmission from imported cases of SARS, especially in hospitals. If the infection is not recognized early and appropriate infection control precautions put in place, extensive transmission can occur. Early detection and ongoing surveillance appears to be the main reason for the lack of transmission from cases in B.C. and the U.S. Those most at risk seem to be family members (19% of cases) and healthcare workers (74% of cases) who have close contact with symptomatic cases. Travel-related cases are few (7%). It is worth noting that there were no reported secondary cases from 2 hospitalized Canadian SARS cases where family members were not permitted to visit and healthcare workers adhered to strict infection control precautions.

Other Sources of Transmission: WHO is aware of concern over the possibility that SARS may be caused by contact with animals. WHO is therefore working closely with the Food and Agriculture Organization of the United Nations (FAO) and the Office International des Epizooties (OIE), to determine whether there is any evidence to suggest that SARS-related disease has occurred in animals. WHO, FAO and OIE have reviewed reports received regarding SARS transmission. To date there is no epidemiological information to suggest that contact with goods, products, or animals shipped from SARS-affected areas has been the source of SARS infection in humans.


 2003 Case Count (cumulative cases) Based on WHO Definitions

By December 31, 2003 the World Health Organization (WHO) received reports of 8098 probable cases (774 deaths) of Severe Acute Respiratory Syndrome (SARS), an atypical pneumonia due to one or more viruses. The first documented case occurred on November 16, 2002 (China). The last reported case in the 2003 epidemic occurred on July 13, 2003 (U.S.). Healthcare workers accounted for 21% of all cases. The world case fatality rate for probable cases was 9.6%. Twenty-six countries reported cases, with the majority of cases occurring in China, Hong Kong, Singapore, Taiwan, Viet Nam, Canada and the U.S. [see epidemic curves]. [ref: World Health Organization]. For a summary of cases by country refer to the WHO summary table.

In the U.S. there were 8 confirmed cases, 19 probable cases and 137 suspect cases reported in 2003. (total 164 cases). No deaths were reported in the U.S. [ref: Centers for Disease Control and Prevention].

In Canada there were 251 probable cases (247 cases in Ontario, 4 cases in British Columbia), with 44 deaths (43 probable, 1 suspect). In addition there were 187 suspect cases (128 in Ontario, 46 in B.C., 6 in Alberta, 4 in PEI, 2 in New Brunswick and 1 in Saskatchewan). The case fatality rate in Canada was estimated at approximately 17.1% of probable cases (10.0% of probable and suspect cases). Most of the case fatalities occurred in patients with underlying illness, and nearly all were elderly patients with the average age being 71 years. There have been no new cases of SARS in Canada since June 12, 2003. [ref: Health Canada].

There were a total of 136 probable cases and 27 deaths in the first Ontario cluster and 111 probable cases with 17 deaths in the second Ontario cluster in 2003.

The Ontario Experience

In Ontario, Public Health officials closed two hospitals in Toronto in March, 2003. The initial cases in Toronto were either travellers from Asia or healthcare workers who had unprotected contact with initial cases before they were aware of SARS. On March 26, the Premier of Ontario declared SARS to be a provincial emergency. It was also made a reportable virulent communicable disease in Ontario. On March 27, 2003 additional measures were put into place in the Greater Toronto Area and Simcoe County, which included limiting visitors to hospitals, restricting patient visits to hospitals, suspending volunteer programs and suspending patient transfers into the city hospitals as well as transfers between health care facilities in the area. On March 31 these measures were extended to all hospitals in Ontario. On May 16, 2003 many of these restrictions were lifted as there had been no new cases of SARS in Ontario since May 4, 2003.

On May 24, health authorities in Canada informed WHO that two clusters of cases of respiratory illness in Toronto were undergoing investigation for respiratory illness, including pneumonia. One cluster involved 5 cases and a second cluster involved 26 cases, including 10 health care workers. One patient undergoing investigation had been linked to both clusters. There was no evidence of widespread public transmission of SARS and all of the new cases under investigation were linked to the original cluster of cases. Hospitals in the Greater Toronto Area were asked to return to heightened infection control protocols in their Emergency departments. These precautions have now been relaxed and there are no current travel advisories due to SARS. For the CCWR report on this second cluster see CCDR Preview, 13 June 2003.

SARS CoV in Laboratory Workers [August/03, December/03]

On August 26, 2003 the World Health Organization confirmed a single case of SARS in a laboratory worker in Singapore, the first case since the end of the world pandemic of SARS.  Acquisition appeared to have been occupational [WHO Website]. On December 11, 2003 a laboratory worker in Taiwan developed symptoms of SARS following laboratory exposure [WHO Website]. There was no transmission related to either of these cases. Laboratory workers can find guidelines for working with SARS in laboratories in the Laboratory Information section of this page (under SARS LINKS).

Post-epidemic SARS in Guangdong, China [December/03 - January/04]

On December 20, 2003 a 32–year–old television producer from Guangzhou, China was hospitalized and placed on isolation with symptoms of pneumonia (onset December 16). Laboratory tests indicated the possibility of SARS CoV infection. Further testing confirmed SARS. All contacts were quarantined and there were no additional cases. For more information on this case:

Since then, three further cases (confirmed in a female restaurant worker and a physician, probable SARS in a business man) surfaced in Guangzhou. All four cases were unrelated. There have been no secondary cases of SARS. For more information:

Post-epidemic SARS-CoV in Beijing, China [April/04]

Confirmed Cases: On March 25, 2004 a 26-year-old female laboratory researcher (who had been working with the SARS virus) developed symptoms compatible with SARS and was hospitalized in Beijing. The researcher's mother, who also assisted in her care, fell ill on April 8 and died on April 22. On April 7, 2004 a 20–year–old nurse who had been caring for the researcher was hospitalized and a few days later was placed in intensive care with SARS-like symptoms (onset April 5). Five contacts of the nurse (her mother, father, aunt, as well as a patient sharing a ward with the nurse and the patient's daughter who accompanied the patient) subsequently developed symptoms (onset April 16 to 19). The ninth case was a 31-year-old male laboratory researcher (same laboratory as the above), who developed symptoms on April 17 and was hospitalized on April 22. These 9 cases were confirmed as caused by the SARS coronavirus by the World Health Organization following extensive review. There have been no new cases since April 19, 2004.

For more information on these cases:

The Public Health Agency of Canada has provided the following documents:



Health Canada epidemiological summaries:



As SARS is not thought to be an airborne infection, research must clarify the need for airborne precautions compared with measures needed to prevent transmission via droplets and contact with body fluids. The need for protective equipment is related to procedures. Consideration needs to be given to equipment that provides a good standard of care and adequate protection while also being affordable and sustainable. Sophisticated procedures, especially those that generate aerosols, greatly amplify the risks of infection. [WHO]

In the meantime, until more is known about the exact mechanisms of acquisition, the Ontario Ministry of Health has provided a series of directives to Ontario hospitals outlining procedures that must be put into place in the event of another SARS outbreak, for high-risk respiratory procedures (outbreak and non-outbreak conditions), and isolation precautions for patients suspected of having SARS. The recommendations for isolation precautions for SARS patients (suspect or confirmed) include:

  • private room, preferably with negative pressure ventilation and anteroom
  • long-sleeved gown
  • N95 mask or equivalent, for which the wearer has been fit-tested
  • hair cover
  • protective eyewear
  • full faceshield
  • gloves

Equipment should be put on in the above order, and removed in reverse order. Training and familiarity with these procedures is an important component of staff protection, as self-contamination during removal of equipment, with subsequent infection, has been documented. Refer to the Ontario directives for complete infection control procedures.

Protecting Canada's Blood Supply

 Health Canada issued formal direction to blood operators on April 10, 2003 as a precaution to protect the blood supply in Canada and recipients from the possible threat of SARS. Although there is currently no evidence of transmission of SARS through blood and blood components, Health Canada has directed blood operators to temporarily defer from [accepting] blood (for a period of 10 days) from persons who have:
- travelled within the previous 10 days to an affected area outside Canada. The affected areas are currently: China, including the Hong Kong Special Administration Region; Hanoi, Vietnam; Singapore and Taiwan;
- been a patient, worked in, or visited a facility that is under quarantine for SARS.



Antibody tests include ELISA (IGM/IGA) to detect antibodies in serum from day 20 after onset of clinical signs. Antibodies have been identified in some patients as early as 14-21 days after onset. Immunofluorescence assays detect antibodies in serum after day 10 of onset. Test is more difficult to perform, requiring live virus in cell culture and an immunofluorescence microscope, limiting its use to reference laboratories.  PCR can detect genetic material of coronavirus in various specimens (blood, stool, respiratory secretions). Several international reference laboratories have developed primers which are being shared on the WHO website. Virus from patients with SARS can be grown in cell culture from respiratory secretions and blood.

Positive laboratory test results indicate that a patient has been recently infected with the coronavirus. Negative tests do not imply that the patient does not have SARS. The sensitivity and specificity of current tests need to be developed further before they can be used to confirm a clinical diagnosis. [Ref: WHO]

For specimen collection from potential SARS patients, refer to "Guidelines for Collecting Specimens from Potential SARS Patients from the CDC.



Public Health Agency of Canada
World Health Organization (WHO)
Centers for Disease Control and Prevention (CDC)
Provincial Information
Ontario Manitoba Newfoundland & Labrador Top
Laboratory Information
Other Information


  • CCDR 15 April 2003 Preliminary Clinical Description of Severe Acute Respiratory Syndrome
  • CCWR 1 May 2003 The War Against an Unknown Pathogen: Rising to the SARS Challenge
  • JAMA 6 May 2003 Clinical Features and Short-term Outcomes of 144 Patients With SARS in the Greater Toronto Area
  • CMAJ 13 May 2003 SARS: the struggle for containment
  • WHO 20 May 2003  Severe acute respiratory syndrome (SARS): Status of the outbreak and lessons for the immediate future
  • CCDR 1 June 2003  Cluster of Severe Acute Respiratory Syndrome Cases Among Protected Health Care Workers - Toronto, April 2003
  • CCDR 15 June 2003  Assessment of In-Flight Transmission of SARS - Results of Contact Tracing, Canada
  • CCDR 1 July 2003  Update - Severe Acute Respiratory Syndrome - Toronto, 2003
  • NEJM 22 April 2004  Evidence of Airborne Transmission of the Severe Acute Respiratory Syndrome Virus



This section will deal with recommendations and links to expert resources that offer planning for the future and the "next season" of SARS, as well as dealing with some of the devastating effects SARS has had on healthcare in Ontario.