  With a simple phenomenological metapopulation model, which characterizes the
invasion process of an influenza pandemic from a source to a subpopulation at
risk, we compare the efficiency of inter- and intra-population interventions in
delaying the arrival of an influenza pandemic. We take travel restriction and
patient isolation as examples, since in reality they are typical control
measures implemented at the inter- and intra-population levels, respectively.
We find that the intra-population interventions, e.g., patient isolation,
perform better than the inter-population strategies such as travel restriction
if the response time is small. However, intra-population strategies are
sensitive to the increase of the response time, which might be inevitable due
to socioeconomic reasons in practice and will largely discount the efficiency.
