Syphilis resurgence in Dublin, Ireland.

A large outbreak of syphilis was reported in Dublin, Ireland, in 2001. The mean age of patients in 2001 was 35 years and 22.5% of patients were HIV-positive. The number of new cases decreased from 2003 on, however, new diagnoses have again increased. All positive syphilis serology results from 2007-09 were identified. Patients were included if they had a newly positive syphilis serology or, in the case of patients with previously treated syphilis, had a four-fold rise in rapid plasma reagin titre. Four hundred and thirty-nine new diagnoses of syphilis were made. The mean age of patients at diagnosis was 35.7 years (range 17-73 years). Four hundred and twelve (93.8%) cases occurred in men. Three hundred and eighty-one (86.8%) cases occurred in men who have sex with men (MSM). The estimated crude incidence rate among MSM is 378.16 per 100,000 population. Where known, 126/421 (28.7%) occurred in HIV-positive patients. Sixty-eight (15.5%) episodes of syphilis infection were diagnosed in patients who had had previously been diagnosed and treated for syphilis; 43/68 (63.2%) cases of re-infection occurred in HIV-positive patients. The rising number of syphilis diagnoses and high associated HIV co-infection rate is concerning and prevention efforts must continue to decrease the number of new syphilis cases.