Background. Severe acute respiratory syndrome (SARS) has impacted heavily on both Canada's society and its health care system. Quite unexpectedly, hospitals and health care workers became facilitators of disease diffusion. This experience has demonstrated the need for a comprehensive disease control strategy. Aims. The aims are threefold. First, to examine the subtle and changing spatial characteristics of SARS during the short but critical period of its rapid spread in the Greater Toronto Area. Second, to make salient three paradoxes, and their associated dilemmas, faced by nurses and other health care professionals challenged with caring for the sick and containing the rapid spread of the disease. Third, to propose some ways of approaching these dilemmas, as well as some broader preventative and mitigating strategies. Methods. The crosscutting concepts of 'clinical uncertainty' and 'flow of human contacts' are used to explain disease transmission characteristics and urban spatial diffusion and to guide the particular strategies developed. Evidence for the paper comes from public health records, governmental and non-governmental health statements and the initial epidemiological research on SARS. Direct insights are also gained from recent first-hand experiences of Toronto's health care system during the crisis. Discussion. The concepts of clinical uncertainty and the flow of human contacts provide in-depth insights that complement the findings of large-scale epidemiological studies, and help operationalize their general calls for enhanced control measures. The comprehensive disease control strategy proposed includes the creation of a hospital infrastructure specific to the containment of biological threats; an advisory coalition of disease control specialists; the development of a biological threat-and-containment simulation laboratory and three specific programmes in patient safety, risk assessment and community mobilization. Conclusion. It is argued that containment alone, while a necessary and urgent priority, cannot be seen as an end in itself and might better be understood as one possible trajectory within a comprehensive problem-solving strategy. The experiences in Toronto may offer insights to other cities and countries that currently lack such strategies and hence may be vulnerable to similar outbreaks of dangerous infectious diseases.
