1. Carlisle and District Primary Care Trust, Carlisle, United Kingdom;
2. Health Protection Agency, Cambridge, United Kingdom;
3. University of Wales, Aberystwyth, Ceredigion, Wales, United Kingdom;
4. Health Protection Agency Centre for Infections, Colindale, London, United Kingdom;
5. Singleton Hospital, Swansea, Wales, United Kingdom;
6. Cumberland Infirmary, Carlisle, United Kingdom;
7. United Utilities, Great Sankey, Warrington, United Kingdom;
8. West Cumberland Hospital, Whitehaven, United Kingdom