A paper prepared by the Science Group: Working Document on Future of SARS, for the Ontario government. April 11, 2003.

POTENTIAL SARS SCENARIOS FOR ONTARIO

1. Elimination of SARS worldwide.

2. Termination of the current SARS outbreak in Ontario. However, recurrence is likely due to reintroduction of SARS from elsewhere or seasonal resurgence.

3. Current outbreak continues with slow increase in cases.

4. Epidemic spread of SARS in the community, with rapid increase in cases.

Note: All of the above scenarios may be modified by changes in virulence or transmissibility of the infectious agent, changes in population behavior or control measures, introduction of effective diagnostic tests, vaccines, and treatments, or presence of the infectious agent in an animal reservoir.

WHICH SCENARIOS ARE MOST LIKELY?

Although scenario 1 is most desirable, the SARS Science Group does not feel that it is likely. The Group is cautiously optimistic, based on current epidemiologic information, and experience in other provinces and developed countries, that we will achieve control of the current outbreak (scenario 2).

However, as has been demonstrated by the 2003 Ontario SARS outbreak, reintroduction of a single SARS case has the capacity to spread infection to health care workers, household contacts, and the community. If reintroduction is not controlled, another outbreak scenario could follow. The disease could also become permanently established at a low level in Ontario, with or without seasonal outbreaks.

Repeated outbreaks or the ongoing transmission of SARS in Ontario would have serious implications for Ontario. The social, economic and political implications for the province (including loss of business and tarnishing of the province's worldwide image) could be dire. Opportunity costs associated with control strategies (i.e., inability to devote resources to other pressing societal issues) would be very large. Finally, an uncontrolled outbreak in Ontario could result in Ontario serving as a reservoir for infection for other provinces or countries.

The SARS outbreak highlights the ongoing need to prepare and protect Ontario society against the ongoing introduction of other novel, virulent, and communicable infectious agents (e.g., pandemic influenza, other emerging infectious diseases). Such preparation would occur through strengthening of the capabilities of frontline clinicians, infection control practitioners, and public health infrastructure and resources.

What are the implications of scenario 3?
The current level of response by the health care and public health systems is not sustainable. Control measures would have to be adjusted in order to reflect trade-offs between feasibility, control, and other consequences. The implications of scenario 3 for the healthcare and public health systems, and the Ontario economy, are enormous and may be similar to the implications associated with scenario 4.

What are the implications of scenario 4?
A rapidly expanding SARS epidemic could quickly affect most parts of the province, and most healthcare facilities. Multiple simultaneous, large outbreaks could occur, with further exacerbation resulting from repeated introduction of cases by infected travelers. The impact of such an event on Ontario society would be enormous. The healthcare system could be overwhelmed. Case fatality rates could rise due to inability to provide optimal care. Considerable societal disruption could occur, and maintaining even essential services could be problematic.