- Correspondence to David Mesher, Public Health England, Centre for Infectious Disease Surveillance and Control, 61 Colindale Avenue, London NW9 5EQ, UK;
- Received 16 September 2014
- Revised 28 October 2014
- Accepted 30 October 2014
- Published in print 1 February 2015.
- Published online 20 January 2015.
- Published first 19 November 2014.
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