Background:
Bathhouses and similar venues have long been identified as high-risk venues for STD and HIV acquisition. Closing them has been suggested as a public health intervention to reduce STD and HIV transmission. Mathematical modeling can aid in comparing STD and HIV incidence and prevalence under alternative policies in a variety of settings involving multiple interacting infectious diseases.

Objective:
To construct a disease transmission model that characterizes STD and HIV transmission with and without bathhouse-like venues for sexual activity.

Method:
We built a single-stage HIV transmission model that generalizes the Bernoulli process model originally developed by Pinkerton and Abramson. Each sex act between partners is treated as a single trial with the probability of HIV transmission being a function of the particular act and condom usage. Members of the population are not identical but are defined by behaviors such as concurrency, ways in which partners are met, and condom usage. We used the Urban Men's Health Study as our primary data source. We are extending this to incorporate acute-phase HIV infection and to a multi-stage Markov process that adds syphilis and other STD transmission to the model.

Result:
We have identified threshold values for the proportion of overall sex acts taking part in bathhouses at which HIV incidence is equivalent whether bathhouses are open or closed—meaning that under some circumstances, HIV incidence can rise and in others it can fall if bathhouses are removed as a potential venue for meeting sex partners.

Conclusion:
Bathhouse closure can either increase or decrease HIV transmission. Determining appropriate values for model parameters can help predict the impact of such an action and aid decision makers.

Implications:
This model helps identify key areas where data or further research is needed to predict the effect of closing bathhouses and similar venues.