HIV and syphilis co-infections and re-infections: trends from Victoria
Since 2009, the Victorian syphilis enhanced surveillance system has been collecting HIV status and syphilis re-infection status for infectious syphilis cases. Baseline data from 2009 showed that 31% of the infectious syphilis cases were HIV positive and 18% reported were re-infections. This suggested that syphilis transmission among a pool of HIV positive MSM was making a considerable contribution to the syphilis epidemic in Victoria. We analysed the data from 2009 to 2012 to determine whether this pattern of transmission is continuing. Notification data for infectious syphilis between 2009 and 2012 were reviewed by HIV infection status, syphilis re-infection status and risk factor exposures.
A total of 1,472 cases of infectious syphilis were notified in the reporting period, 93% were in males (n=1,362) and 79% were in MSM. Thirty per cent (n=435) were HIV positive (94% in MSM). Fifteen per cent (n=217) reported having a syphilis re-infection (93% in MSM; 62% HIV positive). Ninety-nine percent of the HIV positive MSM had a previous episode of syphilis infection compared to 81% of the HIV negative MSM. Among HIV positive MSM, 45% of the syphilis re-infections were diagnosed following doctor suggested screening compared to eight per cent in HIV negative people. For HIV negative MSM, 44% of the re-infections were diagnosed as a result of patient presenting with clinical signs and symptoms compared to 28% in HIV positive MSM.
Surveillance data suggests that the re-infection especially among HIV positive MSM is contributing to the ongoing syphilis epidemic in Victoria. This highlights the importance of continued monitoring of this trend over time. Further research is warranted to better understand this epidemiological trend and to inform the development of public health interventions specifically targeting syphilis among HIV positive MSM.
