Quarantine Strategies to Halt the Spread

of Epidemics Across National Borders


J.F. Williams, Simon Fraser University, Burnaby, British Columbia


Epidemics such as the Severe Acute Respiratory Syndrome (SARS) outbreak can affect people from multiple countries and each nation is anxious to protect itself from future events.  The disease spreads through the population though close contact but when contagious individuals travel they can then transplant the disease to a new city or country.  The goal of this modeling session is to help develop a quarantine strategy against such outbreaks.  Ultimately we would like to know:


1)     How many reported illnesses in country X mean there is a greater than probability P that someone contagious will travel from X to Y?

2)     Is it ever possible to prevent the spread of disease this way or should we simply begin a mass inoculation campaign (if possible) instead?


An understanding of this problem will help policy makers deal with future epidemics.  Accordingly, the objectives of the problem are:


1)     to develop a model for small scale spread of the disease,

2)     to understand the structure of international travel routes and to determine how diseases can spread on them,

3)     to model the delays that are truly inherent in the detection and reporting systems, and

4)     to use the model to determine the dynamics of the disease and the travel routes to create a realistic and useable quarantine strategy.


Data will be provided on the travel networks to aid in the modeling process, but all other data (including data on diseases) will need to be found or estimated by the team.  The discussion in [1] provides a reasonable good starting point for the development of models.




[1] James M. Hyman and Tara Laforce, ̉Modeling the Spread of Influenza Among Cities, Los Alamos Report LA-UR-03-2900 (2003).