ARCHIVED: Learning from SARS: Renewal of public health in Canada – Dr Naylor's response to Minister McLellan


June 15th, 2003

Hon. A. Anne McLellan
Minister of Health
Government of Canada
Ottawa Canada
K1A 0K9

Dear Minister,

Thank-you for your letter of May 12.

The Advisory Committee on SARS and Public Health appreciates your confidence. As you know, we are working on 'lessons learned' from this serious outbreak, and intend to provide advice on strategies and investments that may help improve Canada's response to similar outbreaks in future.

The Committee has thus far met three times, assembled a portfolio of background documents that will be helpful to our reports, made progress through interviews and reviews of available sources in assembling a chronology of SARS , and begun considering options for change in response to the identifies issues. We are continuting to work towards a completion date in August.

As regards your query, the Committee has discussed, reviewed, and agreed on the following response.

The Committee believes effective method of dealing with SARS and most other communicable diseases given current technologies. Absent a transformative improvement in screening methods (e.g. non-invasive pre-symptomatic detection of persons who will later develop SARS), some importation of infectious diseases, including SARS, may occur despite our best precautions. Thus, we believe the focus of governments should be first and foremost on building the necessary public health infrastructure and clinical capacity to contain infectious outbreaks. Local containment and rapid contract tracing is the key both to prevention of exportation and limiting the impact of importation of infectious diseases.


The Committee fully understands why Health Canada has instituted screening of travellers for SARS. Travel screening signifies concrete action by the Government, and control of traffic across our borders falls squarely within the jurisdiction of the Government of Canada. The Government must maintain public confidence regarding the health status of visitors and immigrants to Canada, respond to concerns on the part of provincial governments about importation of SARS, and meet the expectations of bodies such as the World Health Organization. We also understand that officials working in airports may find thermal screening to be an attractive option as it enhances their own senses of safety.

Thermal scanners have been used for hundreds of thousands of travellers in Hong Kong and Singapore. Hundreds of travellers have been detained for secondary temperature measures and more detailed assessments. As we understand it, the yield from this process is at best one suspect SAS case. A deterrent effect from the presence of scanners has been asserted but never proven. Current scanners are in use at the Toronto and Vancouver airports on an evaluation basis.

A 'cherry card' system is also currently used at the Toronto airport as Toronto is a SARS-affected area. All outbound passengers are given a cherry-coloured sheet with health information and three screening questions. Any 'yes' responses at check-in lead to referral to Health Canada nurses for temperature check and an interview.

Inbound passengers to Canada receive a health alert notice can yellow cards with three SARS-screening questions. These cards are currently given out on all inbound flights from Asia but the scope of screening is steadily being expanded to include all inbound flights at all six major international hubs. Those coming from Asia also fill out a traveller contact information form )TCIF) that seeks information on where the passenger will be over the next 2 weeks. At present these cards/forms are retained at each airport, bundled by flight. The TCIF's are given to Health Canada officials a passengers disembark. Passengers proceed past a quarantine officer who determines if any passengers look visibly ill. The completed yellow cards are given to CCRA agents, who call Health Canada nurses if any forms show any 'yes' responses.

As of late last week, it was estimated that 800,000 passengers had been processed through the card systems, scanners or both. About 550 persons have been subjected to secondary checks. To date no SARS cases have been detected by theses screening systems in Canada.

We estimate that tens of millions of dollars have been or will be spent on operationalizing these systems. Unfortunately, symptoms screening by questionnaire will miss individuals with SARS who are untruthful about their symptoms, or who are asymptomatic because they are still in the incubation period. May other infectious diseases have an incubation period or limited symptoms. Symptom-based or thermal screening will never detect such individuals coming into Canada.

The criteria for a SARS WHO travel advisory include exportation of cases. Exportation does not necessarily reflect laxity of outbound or inbound airport screening as persons may be asymptomatic. The only reason why the WHO criterion makes senses is because exportation is a marker for risk on international spread based in turn on: a) the number of incubating cases in the community that have not been tracked and/or quarantined and are therefore travelling, and b) the propensity of persons in the affected communities to travel abroad. Thus as noted above, investments in enhanced local public health measures to isolate or quarantine persons who may spread SARS abroad is likely to be more productive than extensive investments in outbound airport screening. It should be emphasized, moreover, that only a handful of persons worldwide have taken SARS from Canada to other nations.

We also note that any measures must in theory be extended to include land and sea transport. The cost and logistical implications make this an impractical option.

Response to Specific Questions

We turn now to your specific question which we paraphrase: Should the CCRA form amended to provide more space for travellers to list all the countries they have visited? And can we devise generic screening questions for the CCRA from that might enable routine flagging of at-risk persons on entry to Canada?

The answer from the Committee is 'No' on both counts for the following reasons.

We think it will be logistically difficult to have customs officials review lists of ports of calls on forms, especially as those lists could be long and unwieldy for some travellers. The countries or regions that might be flagged as posing a risk for exportation of infectious diseases will change regularly, requiring constant updates to front-line customs officials. As we saw with the WHO travel advisory for Toronto, reasonable people may disagree sharply about when visiting a specific region does or does not pose a risk of importation of disease on return to the port of origin.

On the matter of generic questions for travellers, we have carefully considered the yield form various questions. Among the options that one might logically consider are questions such as: "Have you had fever or chills in the last 7 days?" or " Have you been in contact recently with anyone who has an infectious diseases?" Here again, symptom screening does not overcome the problems posed by incubation periods, untruthfulness on forms, use of anti-pyretics to mask symptoms and so on. Asking about contact with someone who might transmit an infectious disease if far too general. Any questions must track specific diseases. This in turn presupposes that the traveller would recall and recognize signs and symptoms of a particular disease in a person to whom they were exposed, that the traveller would be truthful, and that the list of disease and associated signs or symptoms could be constantly updated and communicated.

Additionally, while the Committee understand the rationale for the yellow card system currently in effect, we view this system as likely to be very low-yield. We are not advocating its discontinuation. We do advocate an early, critical and careful evaluation of this system before it is incorporated into a 'new normal' through modification of the CCRA forms.

We have considered carefully whether a health economic analysis of thermal screening or the card systems would be worthwhile as part of that evaluation, and decided against suggesting that such a study be commissioned. If just one patient slips through and causes an outbreak of SARS, with attendant massive economic impact, then the result will be hugely skewed against the yield of screening. If one case is picked up and we infer that an outbreak is prevented, the balance tips immediately and completely in the other direction. Accordingly, we think the focus should be on determining how many cases of SARS or other infectious disease are detected by these systems (we believe the evidence is already suggesting the yield will be negligible), and in a simple determination of the direct costs of mounting the program (independent of the indirect costs that have been shifted to airlines and travellers, and can only be estimated with great imprecision).

This latter issue, however, leads us back to the conceptual concern that we have about travel screening. The threat posed by the occasional person who brings SARS or a similar disease to Canada is best contained by enhancing local public health measures and instituting an enhanced system of surveillance in doctor's offices and emergency rooms. Deployment of quarantine officers at airports and close co-operation with airlines to identify ill travellers also seems worthwhile. As we saw with the first SARS patient who arrived in British Columbia from Hong Kong, if sick individuals are identified quickly and isolation precautions are taken early, then outbreaks can be contained. And, as we might infer from the history of the initial cluster of SARS in Toronto, if an individual is asymptomatic on entry to Canada, then neither a yellow card system nor thermal screening will prevent an outbreak

Before making additional investments in screening travellers, we believe all levels of Government should be working together to enhance the public health infrastructure to ensure that subsequent outbreaks can be contained rapidly. We believe there should be better education of the public and professionals about public health measure and travel issues in relation to infectious disease. Specifically, the public must be made better aware of the significance of travel histories in understanding infectious disease. This could improve the availability of travel histories to clinicians and public health officials. We also believe that the general public and health care communities should be provided with timely and clear alerts on global, national and local health risks from infectious diseases. Last, we note that many emergency rooms are not well-equipped to deal with patients who are believed to have infectious diseases (e.g. common waiting areas, no negative pressure assessment rooms, weak procedure for handling patients with suspected contagious illnesses, limited access to infection control personnel, etc.).

Currently-supported Measures

Pending and evaluation of the yellow card system as outlined above, we turn finally to what specific measures might be supported by the Committee at present.

First, we support the continuation of Traveller's Contact Information Forms, focusing in the fist instance for areas that are affected by diseases such as SARS. These are a useful alternative to inadequate airline passenger manifests, and may be useful in contact tracing. Whether their yield over time warrants their continuation is still to be determined.

Second, we encourage an increase in the number of quarantine officers who can provide education to airport staff, customs officials and airline personnel concerning the recognition of illness and measures to be taken to contain risk. Close collaboration with airport authorities and airline personnel to clarity their responsibilities and enhance their understanding of these issues is also logical.

Third, we think the CCRA forms could be modified to increase the prominence that the arrival forms give to the warning that travellers should report their entire travel history promptly to a physician if they become ill after the travel.

Fourth, even if formal card systems for screening turn out to be unsupportable, we believe that, on an ongoing basis, both incoming and outgoing passengers could be given handouts with 'Travellers' Health Information' website flagging health risks in different parts of the world, as well as relevant Canadian regulations and procedures. Any such hand-outs could be modified quickly as disease patterns change. Passengers could also be advised to self-identify to customs officials if there is a healath concern, and customs officials in turn would simply re-direct them to quarantine officers. Some consideration will need to be given to the extent to which this type of system is extended beyond airport to points of entrance to Canada via land and water transportation.

In conclusion, Minister, rapid global travel and the biology of infectious diseases mean that some contagious conditions will be imported to Canada on an ongoing basis. We believe it is most important to raise general awareness, and to build capacity for local public health and health system responses that can identify and contain persons at risk. Enhanced measures to help trace incoming travellers form at-risk regions may also be helpful. We advise the Government to explore the development of streamlined and flexible information tools for all travellers. Extant measures for SARS-specific travel screening need early evaluation. Absent strong evidence for disease-specific and/or high-technology alternatives for screening travellers, generic screening through the CCRA forms is unlikely to be helpful.

Best wishes.

Yours sincerely,


On behalf of the National Advisory Committee on SARS and Public Health

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