Estimating the proportion of HIV incidence attributable to gonorrhea and chlamydia among men who have sex with men in the US
Jones J,Weiss K,Mermin J,Dietz P,Gift T,Chesson H,Rosenberg E,Sullivan P,Lyles C,Bernstein K,Jenness S

Estimating the proportion of HIV incidence attributable to gonorrhea and chlamydia among men who have sex with men in the US

This work was presented at the August 2018 National STD Prevention Conference in Washington, DC.

Background
Sexually transmitted infections (STIs) are associated with an increased risk of HIV acquisition and transmission. Men who have sex with men (MSM) are the population with the highest incidence of HIV and STIs in the US. We estimated the proportion of HIV incidence among MSM attributable to infection with the two most common bacterial STIs, Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT). 

Methods
We used a stochastic, agent-based model of a sexual network of MSM with circulating HIV, NG, and CT infections. Relative risk (RR) multipliers, specific to anatomic site of infection, modified the risk of HIV transmission and acquisition based on STI status. We estimated the effect of NG and CT on HIV acquisition and HIV transmission separately. Stable estimates of the individual-level effect of these infections on risk of HIV transmission and acquisition are not available, so a range of plausible RRs was modeled. Each scenario was simulated for ten years. The population attributable fraction (PAF) was determined for each combination of RRs by comparing the incidence in the final year of a scenario to a scenario in which the RRs associated with NG and CT were set to 1.0. Medians and interquartile ranges for the PAF values were calculated. 

Results
NG and/or CT were present in an estimated 11.0% (IQR: 8.2,10.1) to 18.7% (IQR: 17.7,19.4) of HIV transmission events and 12.4% (IQR: 11.4,13.4) to 21.0% (IQR: 20.1,21.8) of HIV acquisition events. Across scenarios, the PAF for HIV transmission ranged from 1.7% (IQR: -0.9,3.9) to 13.0% (IQR: 10.7,15.2) and the PAF for HIV acquisition ranged from 2.0% (IQR: -0.7,4.3) to 13.8% (IQR: 11.7,16.0).

Conclusions
Mathematical modeling indicates that NG and CT have a potentially meaningful effect on HIV incidence among MSM in the United States. Improving STD detection and treatment among MSM could have a substantial effect on reducing HIV incidence.



Downloadable Files:
STD Conference 2018_Jones.pptx