Rectal gonorrhoea and chlamydia among men who have sex with men in coastal Kenya by Ngetsa, C, Heymann, M, Thiong'o, A, Wahome, E, Mwambi, J, Karani, C, Menza, N, Mwashigadi, G, Muturi, M, Graham, S, Mugo, P, Sanders, E