Outbreaks of syphilis among men who have sex with men attending STI clinics between 2007 and 2015 in the Netherlands: a space-time clustering study.

OBJECTIVES: Infectious syphilis (syphilis) is diagnosed predominantly among men who have sex with men (MSM) in the Netherlands and is a strong indicator for sexual risk behaviour. Therefore, an increase in syphilis can be an early indicator of resurgence of other STIs, including HIV. National and worldwide outbreaks of syphilis, as well as potential changes in sexual networks were reason to explore syphilis trends and clusters in more depth. METHODS: National STI/HIV surveillance data were used, containing epidemiological, behavioural and clinical data from STI clinics. We examined syphilis positivity rates stratified by HIV status and year. Additionally, we performed space-time cluster analysis on municipality level between 2007 and 2015, using SaTScan to evaluate whether or not there was a higher than expected syphilis incidence in a certain area and time period, using the maximum likelihood ratio test statistic. RESULTS: Among HIV-positive MSM, the syphilis positivity rate decreased between 2007 (12.3%) and 2011 (4.5%), followed by an increasing trend (2015: 8.0%). Among HIV-negative MSM, the positivity rate decreased between 2007 (2.8%) and 2011 also (1.4%) and started to increase from 2013 onwards (2015: 1.8%). In addition, we identified three geospatial clusters. The first cluster consisted of MSM sex workers in the South of the Netherlands (July 2009-September 2010, n=10, p<0.001). The second cluster were mostly HIV-positive MSM (58.5%) (Amsterdam; July 2011-December 2015; n=1123, p<0.001), although the proportion of HIV-negative MSM increased over time. The third cluster was large in space (predominantly the city of Rotterdam; April-September 2015, n=72, p=0.014) and were mostly HIV-negative MSM (62.5%). CONCLUSIONS: Using SaTScan analysis, we observed several not yet recognised outbreaks and a rapid resurgence of syphilis among known HIV-positive MSM first, but more recently, also among HIV-negative MSM. The three identified clusters revealed locations, periods and specific characteristics of the involved MSM that could be used when developing targeted interventions.

Chlamydia trachomatis IgG seroprevalence in the general population of the Netherlands in 1996 and in 2007: differential changes by gender and age.

OBJECTIVES: Chlamydia trachomatis (CT) reporting rates from sexually transmitted infection clinics and general practitioners have shown a rising trend in the Netherlands. It is unknown to what extent this reflects increased CT transmission or improved case finding. To achieve more insight into the CT epidemic, we explored the CT IgG seroprevalence (a marker of past CT infection) in the general population of the Netherlands in 1996 and in 2007. METHODS: From two population-based studies in 1996 and 2007, serum samples, demographic and sexual behaviour outcomes were examined, including 1246 men and 1930 women aged 15-39 years. Serum CT IgG antibodies were analysed using the Medac CT IgG ELISA test. Multivariate logistic regression analyses explored the seroprevalence and determinants over time. RESULTS: The CT IgG seroprevalence was higher in women than in men (10% vs 6%). Among women aged 25-39 years the seroprevalence was lower in 2007 (9%) than in 1996 (14%; adjusted OR (aOR) 0.6, 95% CI 0.4 to 0.8). There was no statistical evidence of a difference in seroprevalence within birth cohorts. Factors associated with seropositivity were male gender (aOR 0.4, 95% CI 0.3 to 0.7), a self-reported history of CT infection (aOR 5.1, 95% CI 2.6 to 10.0), age 25-39 years (aOR 1.7, 95% CI 1.1 to 2.7), non-Western ethnicity (aOR 2.2, 95% CI 1.4 to 3.3) and ≥ 2 recent sexual partners (aOR 2.2, 95% CI 1.3 to 3.5). CONCLUSIONS: Between 1996 and 2007 the proportion of individuals in the general population with CT IgG antibodies was lower among women aged 25-39 years, but remained similar among younger women and men.

Sex, drugs, and sexually transmitted infections: A latent class analysis among men who have sex with men in Amsterdam and surrounding urban regions, the Netherlands.

BACKGROUND: Men who have sex with men (MSM) are at high risk for sexually transmitted infections (STI) and often have sex while under the influence of drugs (sexualized drug use). We aimed to identify classes of MSM in Amsterdam and in surrounding urban regions with distinctive patterns of sexualized drug use and their association with STI. METHODS: In this cross-sectional study, data on MSM were collected at STI clinics in the Netherlands between September-December 2017. Information on drug use, sociodemographics and sexual risk behavior, including lab-confirmed STI (chlamydia, gonorrhea, syphilis and HIV) was collected and compared between Amsterdam and surrounding urban regions. Latent class analysis was used to identify classes with similar drug use patterns, which were then linked to sexual behavior and STI. RESULTS: We included 4461 MSM who were a median 35 years old (IQR = 27-47) and mostly Dutch (56.9 %). Use of all drugs was more often reported in Amsterdam compared to surrounding regions (p<0.001). We identified four different classes based on sexualized drug use among Amsterdam participants and three classes in surrounding regions. In both regions, polydrug use classes (compared to classes of no drug use; alcohol use; or few, various drugs) were defined by higher numbers of sexual partners (median range 8-15 vs 4-6, respectively) and higher STI prevalence (range 30.5%-31.8% vs 18.6%-22.8%, respectively). CONCLUSION: Given the high prevalence of risk behavior and STIs, MSM in urban settings partaking in sexualized polydrug use might benefit from tailored outreach, screening, and safe sex and drug use interventions.

Evaluating the impact of health reforms in the Netherlands: Assessing the impact of an alcohol ban on sexually transmitted infections in national surveillance data.

BACKGROUND: On 1 January 2014, the minimum age to buy alcohol increased (16-18 years), accompanied by a public awareness campaign (NIX18). Decreases in alcohol consumption are associated with less risky sexual behaviour. This study analyzed the association between the health reforms andChlamydia trachomatis infections (chlamydia) among young heterosexual people. METHODS: Chlamydia positivity rates, age, and gender from all STI-clinic attendees between 16 and 19 years old in the Netherlands of 2010 to 2016 were obtained. Interrupted time-series assessed immediate and gradual trends in chlamydia rates. RESULTS: Among the control group (18-19 year olds) chlamydia rates increased 0.5% each post-ban month (95% Confidence Interval [CI] 1.002-1.008, p = .001). Among 16-17 year olds there was no monthly increase post-ban (Rate Ratio 1.000, 95% CI 0.993-1.007, p = .948). In terms of confounders, only controlling for partner notification dissolved these time trends. CONCLUSIONS: We found that chlamydia rates after the alcohol ban differed between 16-17 year olds and 18-19 year olds. This demonstrates that the health reforms might have affected this secondary outcome, but obtaining certainty using national surveillance data is difficult. Specific studies should be designed, as now changes in chlamydia over time could be explained by STI-clinic policy changes, by changes on an individual level including reduced alcohol consumption or most likely by the combination of these factors.