February 23, 2012
"Reducing rates of partner change and increasing condom usage among gay men are obvious targets for potentially reducing syphilis transmission among gay men," the authors wrote to introduce the current study. They developed an agent-based stochastic model to examine syphilis transmission among a representative population of gay men in Australia. The model then was used to explore the potential impact of changes in sexual behavior over one-month, three-month, and indefinite time frames on syphilis epidemics.
Simulations of interventions indicated that short-term reductions in partner-change rates and increased condom use "would have negligible impact on the long-term trends of syphilis epidemics." In the absence of interventions, the model forecast increasing syphilis prevalence in this population, "with an increase of 80 percent in the number of men infected with syphilis during the next decade." The results also showed, however, that "if changes in sexual behavior are maintained in the long term, then syphilis epidemics can be mitigated." When condom use is sustained at 80 percent in partnerships that are HIV-discordant or of unknown status, syphilis prevalence is estimated to decrease by 9 percent during a 10-year period. If rates of partner acquisition decline by 25 percent, a 22 percent reduction in syphilis prevalence results.
"Interventions promoting partner reduction or increased condom use would be ineffective in the short term and would have limited prospects for success in the long term unless very large changes in behavior are sustained," the authors concluded. "Complementary social research indicates that such long-term changes in behavior are unlikely to be adopted, and therefore other intervention strategies need to be developed to reduce syphilis among gay men."