Air Travel and the Spread of Influenza: Important Caveats
PloS Medicine (2006) 3: 2159-2960.
While air travel contributes to the spread of influenza epidemics, the magnitude of impact is not clear compared to other factors -- crucial issue when considering a flight ban in the context of pandemic planning. Recent modeling efforts simulating the spread of pandemic influenza have concluded that such an intervention would matter little relative to other interventions [1–3]. But this assessment has now been challenged by an observational study of influenza in the winter following the post-9/11/2001 depression in air traffic. Brownstein and colleagues’ study published in the September issue of PLoS Medicine  correlates variations in air traffic volume with patterns of timing and spread in influenza epidemics, based on United States mortality data from nine epidemic seasons between 1996 and 2005. While we find the study interesting, we have identified several important caveats and question the robustness of the conclusions.