April 1, 2003

Canada

Latest Case Counts
Since yesterday, five additional probable cases of SARS and two deaths have been reported in Canada. A total of 58 individuals who meet the probable case definition of SARS have been reported in Ontario and British Columbia, including 6 deaths; 93 individuals who meet the definition of a suspect case of SARS have also been reported in British Columbia, Alberta, Saskatchewan, Ontario, New Brunswick and Prince Edward Island. Since SARS is a diagnosis of exclusion, the status of a reported case may change over time. At the present time, the case fatality rate in Canada is estimated at approximately 4.0% of probable or suspect cases (N=151), which is similar to that reported by other countries, depending on the criteria used to define a SARS case.

Table 1: Cumulative Number of SARS Cases Reported in Canada: April 1, 2003

Summary of Disease Transmission to Date
The Ontario Ministry of Health and Long-Term Care has reported a total of 56 probable cases of SARS. 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 has since been reported. 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. To date, transmission of disease has occurred in household and hospital settings. There is no evidence of transmission in the general community. 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 the two probable cases from British Columbia have been linked to travel-related exposure. The first identified probable case of SARS in British Columbia stayed at the Metropole Hotel, and the second indivdual was exposed to a SARS case in Hong Kong. Both individuals are currently in isolation and there is no evidence of further spread in British Columbia. All of the 12 suspected cases currently under investigation in BC are also associated with travel-related exposures. 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.

Preliminary Descriptive Findings
Given the information currently available, the average age of probable cases in Canada is 46.2 years (n=45, range 2 to 82 years), with 31 females and 20 males. The current number of probable cases by reported symptom onset date and type of exposure is also provided (Figure 1).

Figure 1: Number of probable cases of SARS in Canada by symptom onset date and exposure type from: February 23 to April 1, 2003
(n=45, excluding 13 for whom onset dates or exposure classification are unknown)

Table 2: Known current status of probable cases in Canada: April 1, 2003 (n=23, excluding 35 individuals whose status is either unknown or missing)

Preliminary Epidemiologic Findings
Transmission: Based on the most recent epidemiologic investigations, 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.

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 Manifestiations: The main signs and symptoms seen in cases of SARS include fever (>38.0 degrees Celsius), cough and shortness of breath. Symptoms of an upper respiratory tract infection may not be present. A few cases have developed increasing respiratory distress and require mechanical ventilation. In the majority of hospitalised cases, an infiltrate on chest x-ray and lymphopenia is evident. In addition, thrombocytopenia (<150,000/mm3), elevated creatinine kinase and elevated ALT/AST may be observed. The WHO is coordinating global efforts to better characterize the clinical manifestations of SARS. Because awareness and surveillance of the disease have increased worldwide, an increase in the number of suspected cases is to be expected.

Severity of Illness: Of all of the probable cases reported to date, most remain hospitalised for isolation purposes and only three are now in intensive care. All six deaths have been associated with individuals with underlying illness and all but one occurred in elderly patients. Of 32 probable cases for whom hospitalisation status is known, 3 are currently in intensive care. In addition, two of the three cases that required intubation have since died.

Public Health Measures
Ontario has declared a provincial emergency and SARS is now a reportable diseases under Ontario's Health Protection and Promotion Act. The province has introduced a number of public measures in an effort to contain the spread of SARS. Key public health measures include: extensive contact tracing of persons who may have come in contact with SARS cases, isolation of suspect and probable cases, and voluntary home quarantine for asymptomatic contacts. Isolation wards have been established at hospitals and health care staff are required to observe full airborne and contact precautions. Health care staff across the province are now alerted to SARS and have implemented infection control practices to protect themselves and their patients in an effort to prevent any further infection.

Health Canada is supporting Ontario in its SARS response efforts by providing epidemiologic and infection control expertise, as well as emergency supplies as needed. Health Canada in collaboration with the Provinces and Territories has implemented enhanced surveillance for the detection of SARS cases, alerted laboratories and initiated special laboratory investigations in an effort to identify the cause of SARS. In addition, Health Canada has initiated the first phase of implementing screening procedures for all domestic and international travellers departing from Toronto, in response to the WHO recommendations to prevent travel-related spread of SARS. In addition, due to recent concerns regarding the possibility of transmission of SARS aboard aircraft, Health Canada has also recommended the follow-up of all passengers on flights where a suspect or probable SARS case is identified. For regular updates on public health actions taken by Health Canada, please see the most recent update at:
http://www.sars.gc.ca.

International

Since November 1, 2002, 1809 cases of SARS (1751 outside of Canada) have been reported to the World Health Organization (refer to Table 3). The majority of cases are reported from Guangdong Province and Hong Kong Special Administrative Region of China, Singapore and Hanoi, Vietnam with Hong Kong presently showing the greatest increase in cases. Due to the continued steep rise in the number of SARS cases detected in one apartment building in Hong Kong over the past few days, the WHO reported today that the Hong Kong Department of Health issued an unprecedented isolation order requiring the residents of this complex to remain quarantined at home for the next 10 days. Cases of SARS in other parts of the world have occurred in persons or close contacts of persons who have travelled to these destinations. As of April 1, 2003, 54 deaths have been reported outside of Canada, the majority (34) of which were reported in Guangdong Province of China. The total number of cases and deaths in Guangdong was only recently reported in the WHO cumulative international total and included only data for the period November 16, 2002 to February 28, 2003.

As of March 25, 13 persons with suspected or probable SARS are known to have stayed at the Metropole Hotel in Hong Kong. These cases subsequently became index cases in several countries, including Vietnam, Singapore, the United States, Ireland, and Canada (MMWR Vol 52, No. 12, March 28, 2003). The visitor from mainland China, a medical doctor from Guangdong Province who became ill a week before staying at the hotel, is considered to be the original source of the infection. No further cases have been linked to the hotel.

The majority of cases have occurred in people who have had very close contact with other cases including household contacts and health care workers.

Table 3: Cumulative Number of SARS Cases* and Deaths Reported to WHO:
November 1, 2002 to April 1, 2003