What is the empirical basis for converting banded ordinal data on numbers of sex partners among MSM into a continuous scale level variable? A secondary analysis of 13 surveys across 17 countries

Still trouble with bleeding: Risk factors for HCV transmission in men who have sex with men and behavioural trajectories from 2019 to 2021

OBJECTIVES

To identify sexual/sex-associated risk factors for hepatitis C transmission among men who have sex with men (MSM) and visualise behavioural trajectories from 2019 to 2021.

METHODS

We linked a behavioural survey to a hepatitis C cohort study (NoCo), established in 2019 across six German HIV/hepatitis C virus (HCV) treatment centres, and performed a case-control analysis. Cases were MSM with recent HCV infection, and controls were matched for HIV status (model 1) or proportions of sexual partners with HIV (model 2). We conducted conditional univariable and multivariable regression analyses.

RESULTS

In all, 197 cases and 314 controls completed the baseline questionnaire and could be matched with clinical data. For regression models, we restricted cases to those with HCV diagnosed since 2018 (N = 100). Factors independently associated with case status included sex-associated rectal bleeding, shared fisting lubricant, anal douching, chemsex, intravenous and intracavernosal injections, with population-attributable fractions of 88% (model 1) and 85% (model 2). These factors remained stable over time among cases, while sexual partner numbers and group sex decreased during COVID-19 measures.

CONCLUSIONS

Sexual/sex-associated practices leading to blood exposure are key factors in HCV transmission in MSM. Public health interventions should emphasize the importance of blood safety in sexual encounters. Micro-elimination efforts were temporarily aided by reduced opportunities for sexual encounters during the COVID-19 pandemic.

Estimating Partnership Duration among MSM in Belgium-A Modeling Study

Mathematical modeling is widely used for describing infection transmission and evaluating interventions. The lack of reliable social parameters in the literature has been mentioned by many modeling studies, leading to limitations in the validity and interpretation of the results. Using data from the European MSM Internet survey 2017, we developed a network model to describe sex acts among MSM in Belgium. The model simulates daily sex acts among steady, persistent casual and one-off partners in a population of 10,000 MSM, grouped as low- or high-activity by using three different definitions. Model calibration was used to estimate partnership duration and homophily rates to match the distribution of cumulative sex partners over 12 months. We estimated an average duration between 1065 and 1409 days for steady partnerships, 4-6 and 251-299 days for assortative high- and low-activity individuals and 8-13 days for disassortative persistent casual partnerships, respectively, varying across the three definitions. High-quality data on social network and behavioral parameters are scarce in the literature. Our study addresses this lack of information by providing a method to estimate crucial parameters for network specification.

Social and behavioural determinants of syphilis: Modelling based on repeated cross-sectional surveys from 2010 and 2017 among 278,256 men who have sex with men in 31 European countries

Background

Syphilis case notifications among men-who-have-sex-with-men (MSM) have increased markedly over the past two decades in Europe. We tested several potential factors for this resurgence.

Methods

Self-reported data from two cross-sectional waves of the European MSM Internet Survey (EMIS-2010 and EMIS-2017, N = 278,256 participants living in 31 European countries) were used to fit multivariable hierarchical logistic regression models designed to evaluate potential social, behavioural, and interventional determinants of syphilis diagnosis. Additional multivariable hierarchical negative binomial models investigated determinants of the number of non-steady male condomless anal intercourse (CAI) partners. We tested the hypothesis that more CAI and syphilis-screening are associated with syphilis resurgence, both linked to use of pre-exposure prophylaxis (PrEP).

Findings

Between 2010 and 2017, incidence of syphilis diagnosis in the previous 12 months rose from 2.33% (95%CI: 2.26–2.40) of respondents reporting a syphilis diagnosis in 2010 compared with 4.54% (95%CI: 4.42–4.66) in 2017. Major factors contributing to syphilis diagnosis were living with diagnosed HIV (adjusted odds ratio (aOR) 2.67, 95%CI: 2.32–3.07), each additional non-steady male CAI partner (aOR 1.01, 95%CI: 1.01–1.01), recency of STI-screening (previous month vs no screening, aOR 25.76, 95%CI: 18.23–36.41), selling sex (aOR 1.45, 95%CI: 1.27–1.65), and PrEP use (aOR 3.02, 95%CI: 2.30–3.96). Living with diagnosed HIV (adjusted incidence rate ratio (aIRR) 3.91, 95%CI: 3.77–4.05), selling sex (aIRR 4.39, 95%CI: 4.19–4.59), and PrEP use (aIRR 5.82, 95%CI: 5.29–6.41) were associated with a higher number of non-steady male CAI partners. The association between PrEP use and increased chance of syphilis diagnosis was mediated by STI-screening recency and number of non-steady male CAI partners, both substantially higher in 2017 compared to 2010.

Interpretation

Syphilis cases are concentrated in three MSM population groups: HIV-diagnosed, PrEP users, and sex workers. Behavioural and interventional changes, particularly more non-steady male CAI partners and recency of STI-screening, are major contributing factors for increasing syphilis diagnoses among MSM in Europe.

Funding

European Centre for Disease Prevention and Control.