Epi-Update: Interim Report on the SARS outbreak
in the Greater Toronto Area, Ontario, Canada
April 24, 2003
1. Background
Severe Acute Respiratory Syndrome (SARS), a new atypical pneumonia, originated
in Guangdong Province, China in November 2002. This syndrome appears to have
some association with infection with a novel coronavirus. While isolated travel
related cases have been reported in Greater Toronto Area (GTA) and other parts
of Canada, progression to a large outbreak occurred in Toronto in March 2003,
originating from a single traveler who returned from Hong Kong in late February.
The outbreak now involves more than 250 people in the province of Ontario.
Health Canada is currently working with international partners in investigating
reports of SARS cases exposed in Canada and diagnosed elsewhere. Countries
include Australia, Philippines, United States, Germany and Bulgaria. A summary
of the international investigations associated with travel to Canada will
be reported separately. This interim report describes the current results
of the epidemiological investigation of the SARS outbreak in the GTA.
The outbreak in the GTA has proceeded through five major stages. These are
listed below:
- Spread of SARS infection within the family of the index case;
- Amplification of the SARS outbreak through hospital-based spread;
- Transmission within immediate household members of the health care workers,
patients and visitors to these hospitals;
- Isolated sporadic cases due to limited transmission in the workplace;
- Transmission in an extended family and associated religious group
The following provides an overview of the epidemiology of the outbreak in
the GTA as of April 19, 2003.
2. Spread of SARS infection within the family of the index case
The index case of SARS in Canada (Case A) was a 78-year-old female who was
infected during a stay at a hotel in Kowloon district of Hong Kong between
February 17 and 21, 2003. She returned to Toronto on February 23, 2003; there
was no transmission of SARS to other passengers on her return flight. The
infection spread to her family members, three of whom visited their family
physician who also became ill. Six of the eleven members of this family developed
develop SARS and two died. Poutanen SM et al provide a detailed description
of these cases in the New England Journal of Medicine1.
These events occurred before March 12, 2003, at which time the World Health
Organization (WHO) issued an alert about SARS and initiated global surveillance.
3. Transmission in hospitals
3.1. Hospital A
The son (Case B) of the index case presented with respiratory symptoms at
the emergency room (ER) of hospital A on March 7, 2003. He was managed in
a general observation area of the ER and received a bronchodilator via a nebulizer.
During this time, SARS was transmitted to two other patients who were also
in the ER general observation area (cases C and D).
Case C began to exhibit symptoms of SARS three days later. He was brought
to hospital A on March 16, 2003. Case C was admitted to the ICU and placed
in isolation. On the same day, his wife also became ill. SARS was transmitted
to two paramedics and a fire fighter by case C and to four ER staff, one housekeeper
and seven visitors who were in the ER at the same time. Additionally, the
infection was spread to three other members of the family. The seven ER visitors
transmitted the infection to five household members and other family contacts.
In the ICU, Case C was intubated by a physician who wore a face shield, mask,
gown and gloves when performing the procedure. He did not use precautions
when he was in contact with Case C's wife. He subsequently developed SARS
and transmitted the infection to one member of his family. In total, Case
C infected fifteen other people.
Case D became ill on March 13, 2003 and was admitted to hospital A. Because
he presented with a myocardial infarction, and SARS was not recognized, infection
control precautions were not used. After three days in the CCU, he was transferred
to hospital B. Case D transmitted the infection to 11 people in hospital A,
including a paramedic, ER staff, CCU staff and a CCU patient.
Due to the ongoing spread of infection in the hospital setting and concerns
that this potential for spread would result in more cases in hospital A, hospital
A was closed to new patients and active surveillance for SARS was established.
The crude attack rates in the ER were 13%, the ICU 14% and the CCU 50%.
3.2. Hospital B
Case D was transferred to the ICU of hospital B and was not placed in isolation.
Case D's wife was subsequently admitted to the surgical unit on March 21,
2003. The couple was assumed to be the source of the hospital outbreak. Following
the identification of five staff members ill with SARS, strict infection control
policies were applied. One staff member was a dialysis nurse who worked one
shift while symptomatic. Follow-up with dialysis patients has failed to reveal
any further transmission among this group. A total of nine staff and one patient
were infected by Case D and his wife.
4. Transmission in households
Transmission of SARS in the household settings has resulted in 33 cases.
From the analysis of the hospital A cluster of 129 cases, there were approximately
85 households involved. Transmission to family members occurred in 21 of those
households (24.7%).
5. Sporadic cases in workplaces
There have been three episodes in which occupational transmission of SARS
has been suspected in settings other than health care facilities. In one worksite,
a worker broke quarantine, became symptomatic and worked with one other person
in a small room while symptomatic. This close contact became a probable case
of SARS. Possible exposures have occurred in two other worksites but, at the
time of writing this report, neither has evidence of transmission of SARS.
6. Transmission in an extended family and religious group
The elderly grandfather of a large family was taken to the ER of hospital
A on the evening of March 16, 2003, at the same time that Case C and his wife
were there. Three members of this family developed SARS. The infection subsequently
spread to their extended family. The grandfather died on April 1, 2003. Visitation
for this deceased person occurred on April 3, 2003 and ill family members
were in attendance.
Members of this family are also part of a religious group that engaged in
frequent worship and social activities. This group held two large church events
on March 28 and 29, 2003 attended by 500 and 250 people, respectively. The
attendees at the second event were a subset of those who attended the first
event. Additionally, this family is part of an extensive social network that
includes many extended families.
To date, a total of 31 probable and suspect cases of SARS have been identified
in this cluster. This number includes fourteen members of the index family,
three health care workers and fourteen other members of the religious group.
Active surveillance and quarantine measures are being used to control the
spread of SARS outside of this group.
7. Epidemiological description of the outbreak as a whole
This section provides the descriptive epidemiology of the overall outbreak.
These data are presented as of April 19, 2003. At this time, there were 249
reported cases of SARS of which 129 (52%) were listed as probable.
7.1. Geographic location of residence
Cases of SARS have been reported by four of the five health units in the
Greater Toronto Area (GTA). The City of Toronto and York Region account for
84% of all suspect and probable cases.
7.2. Distribution by Age and Sex
Of the 249 reported cases, 155 (62%) were female. This percentage is the
same for both suspect and probable cases. It most likely reflects the demographics
of workers in the health care system. The distribution by age indicates a
peak among persons age 36 to 64 years. This peak again reflects the population
who work in health care settings, which is one of the largest risk groups
for this outbreak. The mean and median ages are 44.6 and 42.0 years respectively.
There have been 12 reported cases of SARS among children aged 16 and under.
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