Volume 29-09
1 May 2003

[Table of Contents]

THE WAR AGAINST AN UNKNOWN PATHOGEN: RISING TO THE SARS CHALLENGE

Introduction

On 12 March, 2003, the World Health Organization (WHO) issued a global alert in relation to clusters of severe acute respiratory syndrome (SARS), which appeared to be spreading among health care workers in the Hong Kong Special Administrative Region (SAR) of China and Viet Nam (Hanoi City). The WHO recommended that health authorities increase vigilance for the recognition and reporting of any suspected cases of SARS, including atypical pneumonia. In response, Health Canada recommended enhanced surveillance to detect any possible cases of SARS in Canada. On 13 March, 2003, six Canadian cases were identified, comprising a family cluster of five cases and an unrelated case in a traveller.

When SARS was identified in Canada, the public health system was already primed to respond to emerging pathogens. Years of work on pandemic influenza preparedness, in addition to recent cases of avian influenza (H5N1) in Hong Kong, meant that the routine surveillance systems were already in place and sensitized to the possibility of unusual influenza-like illness emerging from Asia. Moreover, the framework on which to implement a timely and comprehensive response had already been established in the form of the federal/provincial/territorial (F/P/T) Pandemic Influenza Committee, diverse working groups that report to this committee, and linkages at the federal level with the Centre for Emergency Preparedness and Response (CEPR) and the F/P/T communications network, as well as the Council of Chief Medical Officers of Health.

The Canadian response was initiated immediately upon notification of potential cases of SARS. The Pandemic Influenza Committee met by teleconference and began identifying and contacting other partners, including the Council of Chief Medical Officers of Health, that would be critical to the development of an appropriate response. The formation of national working groups on surveillance, clinical management, infection control, laboratory issues, and public health measures and the establishment of teams focusing on the collection and dissemination of national and international epidemiologic data enabled the concurrent development of resources and the division of labour essential to managing this emerging situation. On 16 March, 2003, Health Canada's Emergency Operation Centre was mobilized to support and coordinate daily teleconference calls with international, national and F/P/T stakeholders. This work is ongoing.

This article provides a summary of the current epidemiology of SARS and a description of the actions that have taken place to date to manage this emerging situation in Canada.

Epidemiology of SARS in Canada

Canadian SARS case definitions for both probable and suspect cases as well as updated epidemiologic information are available on the Health Canada SARS Website (www.sars.gc.ca). As of 6 April, 2003, there were 90 probable cases and 127 suspect cases of SARS reported in Canada. The majority of cases have occurred in Ontario, specifically the Greater Toronto Area (GTA). Figure 1 shows the epidemic curve of probable cases.

To date, all identified probable cases of SARS have been linked to travel-related exposures, exposure in a hospital or health care related setting, and household exposures. The majority of cases in Canada (74.4%) have been attributed to exposure in a hospital or health care setting. Only 6% of cases have travel-related exposures; the remaining cases have household exposure. Currently, there is no evidence of transmission in the general community. Four generations of transmission have been documented. The index case in Ontario was a travel-related case who, upon returning to Canada, transmitted the illness to family members. Cases were subsequently reported in the hospital where the family members received care. More recently, cases were reported in household contacts of the hospital-associated cases.

While 17% of probable cases have been discharged from hospital, the clinical condition of 67% of cases is described as stable or improving. As of 6 April, 2003, there have been nine fatalities. The overall Canadian case fatality rate for SARS (probable and suspect cases) is estimated to be 4.1%. The majority of the fatal cases have been in elderly people (over 70 years of age), and most occurred in patients with underlying illness.

It is difficult to conclusively determine the incubation period of the etiologic agent, given the fact that many of the probable cases may have had multiple exposures, but the current estimated mean incubation period is 4 days (estimated range 2 to 10 days).

A summary of the clinical presentation of SARS based on the first 10 cases identified in Canada has recently been published⁽¹⁾.

Health Canada's National Response

National Outbreak Coordination and Management

The Centre for Infectious Disease Prevention and Control (CIDPC), in collaboration with the CEPR, is coordinating, investigating and managing the SARS outbreak at the national level and is providing technical support, as requested, at the provincial and local levels. In addition, given the global nature of this outbreak, the CIDPC is participating in various international epidemiologic investigations.

The CIDPC is facilitating the sharing of information by various stakeholders to allow for a coordinated national investigation of the SARS outbreak. Five national working groups were formed with the express purpose of synthesizing available information and producing documents such as epidemiologic reports, guidelines, and information sheets. Members of the groups are experts at the F/P/T and local levels in public health, infectious diseases, microbiology, infection control, and epidemiology. There is a coordinated approach to the working groups to allow consultation with other working groups on overlapping issues.

All the working groups recognized that documents would need to be developed based on the current knowledge and that there are significant gaps in that knowledge, including the absence of an etiologic agent. Given the numerous gaps, it was acknowledged that all documents developed by the groups were subject to change pending the availability of more comprehensive and conclusive data.

The surveillance working group is responsible for determining case definitions, setting up the structure for enhanced surveillance of SARS, and liaising with other international agencies conducting surveillance of SARS. The group also reviews the available epidemiologic information regarding SARS to provide evidence for issues such as incubation periods and modes of transmission. This group is working with provinces and territories and liaises with the laboratory working group to facilitate linking epidemiologic and laboratory data for a better understanding of the epidemiology of SARS.

The public health measures working group is responsible for developing guidelines to facilitate a consistent, optimal response to SARS by the public health community. Public Health Management of SARS Cases and Contacts contains guidance on the public health management of SARS probable and suspect cases, and also includes information on the management of people under investigation. Included is information on periods of isolation, components of active daily surveillance, and information on contact follow-up.

The infection control working group is providing expert consultation regarding infection control measures used to control SARS. The working group has developed guidelines and fact sheets for a variety of settings, including institutional, outpatient, and community settings. This working group has also made recommendations on the use of specific equipment, such as masks and respiratory equipment and devices.

The clinical working group is responsible for providing a clinical description of SARS cases and developing guidelines on their clinical management, including treatment guidelines and hospital discharge criteria. This working group liaises with Health Canada's Special Access Program (SAP) to facilitate a mechanism providing clinicians with access to oral and intravenous ribavirin for patients who meet the SARS case definition. The SAP has also implemented active surveillance for adverse drug reactions related to ribavirin, to ensure that ongoing, timely feedback can be provided to attending clinicians.

Although there is no evidence that SARS can be transmitted through blood, blood safety is a paramount concern. Canadian Blood Services and HÉMA-QUÉBEC (CBS/H-Q) currently have a number of measures in place that minimize the possibility of transmitting SARS through blood. Every donor's temperature is taken before he or she gives blood. If a donor's temperature is above normal, the individual is not permitted to donate blood. Before donating, donors answer a number of questions about their general health status. If a donor is not healthy, he or she is not permitted to donate. In addition, if public health authorities become aware that an individual with SARS has donated blood within the 10 days before the onset of symptoms of SARS, CBS/H-Q should be contacted immediately for withdrawal of blood/blood components and for other public health actions, as necessary.

Laboratory

The etiologic agent responsible for SARS is unknown, and many Canadian laboratories are working collaboratively to determine the causative agent. Members of the Canadian Public Health Laboratory Network (CPHLN) are testing for conventional causative agents, while Canada's National Microbiology Laboratory in Winnipeg is focusing on identifying unknown causative agents. Samples from people suspected of having SARS are provided to the laboratory and form an important part of the process of identifying viruses and other agents present in samples. Findings are shared among the CPHLN to assist the collective effort. As of 4 April, 2003, two viruses had been identified by the network of laboratories: human metapneumovirus and coronavirus. The particular coronavirus linked to SARS is felt to be unique. The significance of these two viruses in the etiology of SARS is unclear at present. Laboratory safety issues and the safe transportation of specimens have also been addressed.

Travel

The CEPR is coordinating and managing Canada's efforts in international travel-related and quarantine issues regarding SARS. The CEPR has issued travel advisories related to SARS and has advised that people planning to travel to the City of Hanoi, Viet Nam, the People's Republic of China, including the Hong Kong SAR, Taiwan, and Singapore should defer all travel until further notice.

The CEPR has also developed and is distributing, in partnership with other agencies, Health Alert Notices (yellow cards) to incoming international air travel passengers at all Canadian international airports. Quarantine officers, deployed to Pearson, Vancouver, and Dorval airports, have met more than 200 flights and distributed over 75,000 Health Alert Notices to incoming passengers. In addition, Health Alert Notices (cherry cards) are being distributed to outgoing international air travel passengers at Toronto's Pearson International Airport.

As well, the public health measures working group has developed SARS and Air Travel Guidelines in response to a need for recommendations regarding the follow-up of passengers if SARS is identified in someone who has traveled on a plane. The CEPR is involved in obtaining flight manifests from airline operators when it has been determined that a case of SARS has traveled on an international flight. Once these have been obtained, CEPR distributes the manifests to the provinces and territories for appropriate public health follow-up. In addition, infection control guidelines for air flight cabin crew, aircraft cleaning crew, airport staff, and quarantine officers have been produced.

Workplace Safety

The Workplace Health and Public Safety Programme (WHPSP) provides advice and consultation on appropriate occupational health and safety measures pertaining to SARS for federal employees in Canada and around the world. The program has developed advisories for federal workers based on the most current available scientific and epidemiologic information. Federal employers use the advisories to assist them in protecting the health and safety of workers. The WHPSP's medical teams provide information sessions for managers and workers in workplaces, including airports across the country.

A complete list of documents, including epidemiologic updates, guidelines, and fact sheets can be found at Health Canada's SARS Website (www.sars.gc.ca).

Conclusion

Because of the non-specific symptoms of the SARS prodrome, the lack of an etiologic agent, and the diversity in experiences with SARS across Canada, the formulation of a single set of appropriate recommendations for the control of SARS has been challenging. There is a need to enact control measures that err on the side of caution in order to “capture” those who are most likely to have or to develop SARS without unduly restricting personal freedoms and depleting hospital and public health resources.

SARS has affected the global community with both human and economic costs. Canada's response to the SARS outbreak is ongoing. Unprecedented measures have been taken to support public health in affected provinces, particularly Ontario. Although Canada has had the misfortune of being one of the first countries outside of South-East Asia to be affected by SARS, it is fortunate in having established networks, such as the Pandemic Influenza Committee and the Council of Chief Medical Officers of Health, to quickly identify and implement outbreak control measures in order to contain the spread of this disease.

Reference

1.    Identification of severe acute respiratory syndrome in Canada. New England Journal of Medicine. URL: <http://content.nejm.org /
cgi/reprint/NEJMoa030634v1.pdf>.

Source:     Immunization and Respiratory Infections Division, Centre for Infectious Disease Prevention and Control, on behalf of Health Canada.

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