Publication Type: Journal Article Authors: Evans, H. E.; Tsourapas, A.; Mercer, C. H.; Rait, G.; Bryan, S.; Hamill, M.; Delpech, V.; Hughes, G.; Brook, G.; Williams, T.; Johnson, A. M.; Singh, S.; Petersen, I.; Chadborn, T.; Cassell, J. A. Source: Sex Transm Infect, Volume 85, Number 7, p.543-9 (2009)