  Background: The global spread of the severe acute respiratory syndrome (SARS)
epidemic has clearly shown the importance of considering the long-range
transportation networks in the understanding of emerging diseases outbreaks.
The introduction of extensive transportation data sets is therefore an
important step in order to develop epidemic models endowed with realism.
Methods: We develop a general stochastic meta-population model that
incorporates actual travel and census data among 3 100 urban areas in 220
countries. The model allows probabilistic predictions on the likelihood of
country outbreaks and their magnitude. The level of predictability offered by
the model can be quantitatively analyzed and related to the appearance of
robust epidemic pathways that represent the most probable routes for the spread
of the disease. Results: In order to assess the predictive power of the model,
the case study of the global spread of SARS is considered. The disease
parameter values and initial conditions used in the model are evaluated from
empirical data for Hong Kong. The outbreak likelihood for specific countries is
evaluated along with the emerging epidemic pathways. Simulation results are in
agreement with the empirical data of the SARS worldwide epidemic. Conclusions:
The presented computational approach shows that the integration of long-range
mobility and demographic data provides epidemic models with a predictive power
that can be consistently tested and theoretically motivated. This computational
strategy can be therefore considered as a general tool in the analysis and
forecast of the global spreading of emerging diseases and in the definition of
containment policies aimed at reducing the effects of potentially catastrophic
outbreaks.
