Contingency planning for a deliberate release of smallpox in Great Britain--the role of geographical scale and contact structure.
BACKGROUND
In the event of a release of a pathogen such as smallpox, which is human-to-human transmissible and has high associated mortality, a key question is how best to deploy containment and control strategies. Given the general uncertainty surrounding this issue, mathematical modelling has played an important role in informing the likely optimal response, in particular defining the conditions under which mass-vaccination would be appropriate. In this paper, we consider two key questions currently unanswered in the literature: firstly, what is the optimal spatial scale for intervention; and secondly, how sensitive are results to the modelling assumptions made about the pattern of human contacts?


METHODS
Here we develop a novel mathematical model for smallpox that incorporates both information on individual contact structure (which is important if the effects of contact tracing are to be captured accurately) and large-scale patterns of movement across a range of spatial scales in Great Britain.


RESULTS
Analysis of this model confirms previous work suggesting that a locally targeted 'ring' vaccination strategy is optimal, and that this conclusion is actually quite robust for different socio-demographic and epidemiological assumptions.


CONCLUSIONS
Our method allows for intuitive understanding of the reasons why national mass vaccination is typically predicted to be suboptimal. As such, we present a general framework for fast calculation of expected outcomes during the attempted control of diverse emerging infections; this is particularly important given that parameters would need to be interactively estimated and modelled in any release scenario.
House
Thomas
T
Warwick Mathematics Institute and Department of Biological Sciences, University of Warwick, Coventry, UK. T.A.House@warwick.ac.uk
Hall
Ian
I
Danon
Leon
L
Keeling
Matt J
MJ
D023482:Bioterrorism; D002959:Civil Defense; D006801:Humans; D017053:Infection Control / Q000379:methods*; D015233:Models, Statistical; D012899:Smallpox / Q000453:epidemiology* / Q000517:prevention & control* / Q000635:transmission; D006113:United Kingdom; D014611:Vaccination / Q000379:methods