travel). Indeed, arriving travellers might be required to show a certificate of vaccination with a new pandemic vac- cine.
The missing and suboptimal nature of some of the travel data shown in Table 1 is problematic. There is a need for regional agencies to encourage improved data collection and publication by PICTs so that studies such as the one reported here can be undertaken with more realism.
Finally we note that this work has not assessed the value to policy makers of island nations in presenting "escape probabilities" in the way that we have. It could be that to use a mandated travel reduction intervention, policy mak- ers would need to have indications of much higher rates of success than thresholds of 50% (as used in Table 1). They may also need indications of the potential number of hospitalisations prevented and lives saved before there is political and popular acceptance of the policy (e.g. as calculated from case fatality ratios in other countries).
Conclusion These results suggest that relatively few island nations could successfully rely on intensive travel volume restric- tions alone to avoid the arrival of pandemic influenza. Therefore most island nations will need to plan for multi- ple additional interventions (e.g., screening and quaran- tine) to raise the probability of remaining pandemic free.
Competing interests The authors declare that they have no competing interests.
Authors' contributions This study was conceived by NW and MB. ME developed the modelling approach and the mathematics. MS designed the software. NW collected the input data. All authors contributed to drafts of the manuscript.
Additional file 1
"Technical Appendix: Formulae for considering pandemic influenza importation into islands". The technical appendix provides the detailed formulae data for the model used for assessing pandemic influenza impor- tation into islands. Click here for file [http://www.biomedcentral.com/content/supplementary/1471- 2334-9-160-S1.DOC]
Two of the authors (NW and MB) have been assisted by a Centers for Dis- ease Control and Prevention (USA) grant for research work on pandemic influenza control at borders (i.e., grant: 1 U01 CI000445-01).
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Pre-publication history The pre-publication history for this paper can be accessed here:
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