  We present a study of the worldwide spread of a pandemic influenza and its
possible containment at a global level taking into account all available
information on air travel. We studied a metapopulation stochastic epidemic
model on a global scale that considers airline travel flow data among urban
areas. We provided a temporal and spatial evolution of the pandemic with a
sensitivity analysis of different levels of infectiousness of the virus and
initial outbreak conditions (both geographical and seasonal). For each
spreading scenario we provided the timeline and the geographical impact of the
pandemic in 3,100 urban areas, located in 220 different countries. We compared
the baseline cases with different containment strategies, including travel
restrictions and the therapeutic use of antiviral (AV) drugs. We show that the
inclusion of air transportation is crucial in the assessment of the occurrence
probability of global outbreaks. The large-scale therapeutic usage of AV drugs
in all hit countries would be able to mitigate a pandemic effect with a
reproductive rate as high as 1.9 during the first year; with AV supply use
sufficient to treat approximately 2% to 6% of the population, in conjunction
with efficient case detection and timely drug distribution. For highly
contagious viruses (i.e., a reproductive rate as high as 2.3), even the
unrealistic use of supplies corresponding to the treatment of approximately 20%
of the population leaves 30%-50% of the population infected. In the case of
limited AV supplies and pandemics with a reproductive rate as high as 1.9, we
demonstrate that the more cooperative the strategy, the more effective are the
containment results in all regions of the world, including those countries that
made part of their resources available for global use.
