1. Carlisle and District Primary Care Trust, Rosehill, Carlisle, United Kingdom;
2. Communicable Disease Surveillance Centre, London, United Kingdom;
3. University of Wales, Aberystwyth, Ceredigion, Wales, United Kingdom;
4. Singleton Hospital, Swansea, Wales, United Kingdom;
5. Cumberland Infirmary, Carlisle, United Kingdom;
6. United Utilities, Great Sankey, Warrington, United Kingdom;
7. West Cumberland Hospital, Whitehaven, United Kingdom