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Severe Acute Respiratory Syndrome (SARS):
Preliminary Epidemiological Findings as of
April 4, 2003
Summary of Disease Transmission among Probable Cases in Canada:
In Ontario, where nearly all of the probable cases in Canada have been reported,
it is believed that four generations of transmission have occurred. 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.
Upon return to Canada, disease transmission occurred in four members of the
immediate and extended family. A physician who had close contact with members
of this family was also diagnosed with SARS. Following this, cases were reported
in individuals in a hospital setting where some of the first cases were treated.
Most recently, SARS has been reported in a few of the household contacts of
these hospital-associated cases.
Isolated cases of travel-related exposures have also been identified in
Ontario and British Columbia. An isolated case in Ontario was reported in
an individual who had travelled to Asia, but did not stay in at the Metropole
Hotel. Reports of all probable cases from British Columbia have also been
linked to travel-related exposures in Hong Kong. All are currently in isolation
and there is no evidence of further spread in British Columbia. A Canadian
with SARS [not counted in the official Canadian case count], who is currently
hospitalised in Hong Kong, also stayed at the Metropole Hotel.
Nearly all of the probable cases of SARS in Ontario that occurred in individuals
outside of the initial family cluster have been linked either directly or
indirectly back to exposure to the first hospitalised case of SARS, on March
7, 2003. It is believed that disease transmission occurred mainly as a result
of person-to-person contact. The initial hospital-associated cases are thought
to have contracted the illness as a result of unprotected contact with the
initial cases prior to the recognition of SARS. Subsequent transmission may
have then occurred between households of these hospital-associated cases,
and between other healthcare workers. To date, there has been no evidence
of transmission in the general community. Furthermore, there is presently
no evidence to suggest that disease transmission occurs prior to the onset
of fever in a suspected or probable case of SARS.
Preliminary Descriptive Findings:
Given the information available as of April 4, 2003, the average age of probable
cases in Canada is 45.6 years (n=52, range 2 to 82 years), with 37 females
and 20 males. The current number of probable cases by reported symptom onset
date and type of exposure is also provided (Figure).
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Estimated Incubation Period:
While it is difficult to conclusively determine the incubation period of the
etiologic agent, given the fact that many of the probable cases in Ontario
may have multiple exposures, the current estimated mean incubation period
is 4 days (estimated range 2 to 10 days).
Clinical Manifestations:
A summary of the clinical presentation of SARS based on the first 10 cases
identified in Canada has recently been published (source: New England Journal
of Medicine, http://content.nejm.org
/cgi/reprint/NEJMoa030634v1.pdf). Listed in order of observed frequency
are fever (10/10), nonproductive cough (10/10), shortness of breath (8/10),
malaise (7/10), diarrhea (5/10), chest pain (3/10), headache (3/10), sore
throat (3/10), myalgias (2/10), and vomitting (1/10). Lymphopenia, elevated
lactate dehydrogenase levels, elevated aspartate amino-transferase levels
and elevated creatinine kinase levels were also reported. The World Health
Organisation is currently coordinating global efforts to better characterize
the clinical manifestations of SARS.
Severity of Illness:
Of all the probable cases reported on April 4, 2003, most remain hospitalised
for isolation purposes. Shown in the Table is the reported known status of
40 probable cases of SARS that are currently hospitalised, or were subsequently
discharged, as of April 4, 2003. Please note that these numbers are based
on preliminary data, and will be updated accordingly as more information becomes
available. All seven deaths reported to date have been associated with individuals
with underlying illness and all but two have occurred in elderly patients
over the age of 70.
Table: Reported known status of currently hospitalised or subsequently
discharged probable cases of SARS in Canada: April 4, 2003
(n=40, excluding 7 deaths and 27 individuals whose status is currently unknown)
| Status |
Number of Cases |
Proportion |
| Discharged |
8 |
20 % |
| Improving |
6 |
15 % |
| Stable |
22 |
55 % |
| Deteriorating |
2 |
5 % |
| Critical |
2 |
5 % |
| Total Number of Probable Cases with Known Status,
Currently Hospitalised or Discharged |
40 |
100 % |
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