Individual and Population Level Effects of Partner Notification for Chlamydia trachomatis

10.1371/journal.pone.0051438PLoS ONE712

Changing patterns of undiagnosed HIV infection in the Netherlands: Who benefits most from intensified HIV test and treat policies?

Objectives: To estimate HIV prevalence, the number of people living with HIV/AIDS (PLWHA) and the undiagnosed proportion in the Netherlands for 2012, and to compare these with published 2007 estimates. Design: Synthesis of all available data sources. Methods: Multi-Parameter Evidence Synthesis (MPES) was used to obtain estimates in mutually exclusive key populations at higher risk in three geographical regions (Amsterdam, Rotterdam, rest of the Netherlands). Data sources included HIV prevalence surveys, diagnoses at STI clinics, and registered cases in HIV care. Group specific estimates were reported as Bayesian posterior medians and 95% credible intervals (CrI). Results: The 2012 model estimated 24,350 PLWHA (95% CrI 20,420-31,280) aged 15-70 years; 2,906 (+14%) more than in 2007. The estimated population HIV prevalence was 0.20% (95% CrI 0.17-0.26%). The overall proportion of undiagnosed HIV was lower in 2012 (34%, 95% CrI 22-49%) compared to 2007 (40%, 95% CrI 25-55%). After MSM, migrants from sub-Saharan Africa and the Caribbean formed the largest groups of PLWHA, but proportions of undiagnosed HIV remained high in these groups, 48% and 44% respectively. Amsterdam had lowest proportions undiagnosed for most key populations at higher risk, including MSM and migrants. Conclusions: In 2012, the number of PLWHA was higher compared to 2007, while the proportion of undiagnosed HIV was lower, especially among MSM. Higher HIV testing rates, earlier treatment, and an improved life expectancy may explain these differences. HIV interventions need to be expanded in all key populations at higher risk, with special focus on migrants and key populationsliving outside of Amsterdam. Copyright

Longitudinal Patterns of Sexually Transmitted Infection Risk Based on Psychological Characteristics and Sexual Behavior in Heterosexual Sexually Transmitted Infection Clinic Visitors

Sources of Funding: The Strategic Programme (SPR) of the National Institute for Public Health and the Environment (RIVM) provided funding for this study (project number S/113004/01/IP).Peer reviewedPublisher PD

Dispersal of Venturia inaequalis ascospores and disease gradients from a defined inoculum source

Aerial concentration of ascospores of Venturia inaequalis and incidence of apple scab were monitored in an orchard during the ascospore release seasons in 1999, 2000 and 2001 on susceptible (Jonagold) and moderately resistant (Schone van Boskoop) apple cultivars. A 1-ha orchard was divided into an inoculum source block (approximately 0.34 ha) and an inoculum-free block (approximately 0.66 ha) where inoculum was excluded by covering the soil surface with polythene sheets. Ascospore numbers and disease incidence were measured within the inoculum-free block at different distances from the inoculum block. Ascospores were sampled with three Burkard volumetric spore traps located at 0, 21 and 45 m from the border of the inoculum block. To determine the incidence of infection, clusters of leaves were assessed at six distances from the border of the infected source from the time the first symptoms appeared. Each year, the aerial ascospore concentration significantly decreased with distance from the source, as did the incidence of infected clusters. Cultivar susceptibility to apple scab markedly influenced incidence of infected clusters and disease gradients. The effect of horizontal distance from the source was identifiable up to 18 m and 33 m for cv. Schone van Boskoop and cv. Jonagold, respectively, beyond which disease was negligible. The disease gradients for cultivar Jonagold in 1999, 2000 and 2001 were well described by an exponential model with gradient coefficients of -0.036, -0.042 and -0.047, respectively. The number of infected clusters at the source border for this cultivar differed significantly over the 3 years. A single exponential model with a gradient coefficient of -0.035 adequately described the disease gradients for cultivar Schone van Boskoop in each of the 3 years. Further analysis showed highly significant correlations (r > 0.85, P <0.01) between the annual cumulative spore catches and the annual mean number of infected leaf clusters in each year and for both cultivars. The aerobiological and epidemiological implications of these findings are discussed

Transmission dynamics of Chlamydia trachomatis affect the impact of screening programmes

10.1016/j.epidem.2010.04.002Epidemics23123-13

Analysis of summer epidemic progress of apple scab at different apple production systems in the Netherlands and Hungary

Two, 4-year studies on summer epidemic progress of apple scab were conducted at Randwijk, the Netherlands, from 1998 until 2001 and at Eperjeske, Hungary, from 2000 until 2003. Disease assessments were made on scab-susceptible cv. Jonagold. A range of nonlinear growth functions were fitted to a total of 96 disease progress curves (3 treatment classes x 2 plant parts x 2 disease measures x 4 years x 2 locations) of apple scab incidence and severity. The three-parameter logistic model gave the most consistent fit across three treatment classes in the experiment (integrated, organic-sprayed, and organic-unsprayed). Parameters estimated or calculated from the three-parameter logistic function were used to analyze disease progress. These were disease incidence and severity on the day of the first assessment (Y-s); final disease incidence or upper asymptote for incidence (Y-if) or severity (Y-sf); fruit incidence and severity on day 40, after which no new lesions on fruits appeared (Y-40); leaf incidence and severity on day 75, at which shoot growth stopped (Y-75); relative (beta) and "absolute" (theta) rates of disease progress; inflection point (M); and area under the disease progress curve (AUDPC(5)) standardized by the duration of the total epidemic. Comparisons among disease progress curves were made by Correlation and factor analysis followed by Varimax rotation. There were large differences but high positive correlations among the parameters Y-s, Y-f, theta, and AUDPC(5) across the three treatment classes. In the factor analysis, two factors accounted for more than 85% of the total variance for both incidence and severity. Factor I gave an overall description of epidemic progress of both scab incidence and severity and included the parameters Y-f, Y-40, Y-75, theta, and AUDPCs. Factor 2 identified a relationship between the relative rate parameter (P) and the inflection point (M) for severity and a relationship between disease incidence and severity. For an integrated or an organic orchard, theta, AUDPC(5), and one of Y-f or Y-75 (because of the link with host phenology) can characterize apple scab epidemics during summer. Based on these findings, improved scab management approaches were provided for integrated and organic apple production systems

Infectious disease transmission as a forensic problem: Who infected whom?

Observations on infectious diseases often consist of a sample of cases, distinguished by symptoms, and other characteristics, such as onset dates, spatial locations, genetic sequence of the pathogen and/or physiological and clinical data. Cases are often clustered, in space and time, suggesting that they are connected. By defining kernel functions for pairwise analysis of cases, a matrix of transmission probabilities can be estimated.We set up a Bayesian framework to integrate various sources of information to estimate the transmission network. The method is illustrated by analysing data from a multi-year study (2002-2007) of nosocomial outbreaks of norovirus in a large university hospital in the Netherlands. The study included 264 cases, the norovirus genotype was known in approximately 60 per cent of the patients. Combining all the available data allowed likely identification of individual transmission links between most of the cases (72%). This illustrates that the proposed method can be used to accurately reconstruct transmission networks, enhancing our understanding of outbreak dynamics and possibly leading to new insights into how to prevent outbreaks

Longitudinal Patterns of Sexually Transmitted Infection Risk Based on Psychological Characteristics and Sexual Behavior in Heterosexual Sexually Transmitted Infection Clinic Visitors

Background Great heterogeneity in sexually transmitted infections (STI) risk exists, and investigating individual-level characteristics related to changes in STI risk over time might facilitate the development and implementation of effective evidence-based behavior change interventions. The aim of this study was to identify longitudinal patterns of STI risk based on psychological and behavioral characteristics. Methods A longitudinal study was conducted among heterosexual STI clinic visitors aged 18 to 24 years. Latent classes based on behavioral and psychological characteristics at baseline, and transitions from 1 latent class to another at 3-week, 6-month, and 1-year follow-up, were identified using latent transition analysis. Results Four latent classes were identified that could be differentiated by psychological and behavioral characteristics and STI risk: overall low-risk (10%), insecure high-risk (21%), condom-users (38%), and confident high-risk (31%). Although the majority of the total study population did not move to another latent class over time, the size of the overall low-risk group increased from 10% at baseline to 30% after 1 year. This was mainly due to transitions insecure high-risk, condom-users, and confident high-risk class at 3-week follow-up to the overall low-risk class at 6-month follow-up. Conclusions Distinct subgroups among heterosexual STI clinic visitors can be differentiated from each other by multiple psychological and behavioral characteristics, and these characteristics reflecting the risk of acquiring STI are consistent over the course of 1 year in most individuals. An integral approach, adapting behavioral interventions to match multiple psychological and behavioral characteristics of high-risk subgroups, might be more effective in controlling STI transmission. © Lippincott Williams & Wilkins

Sexually transmitted infections, including HIV, in the Netherlands in 2013.

In 2013, more people were tested for sexually transmitted infections (STI) at Dutch STI clinics than in previous years. Although the percentage of people with an STI showed a slight decrease (0.4 per cent) for the first time since 2007, it remained high at 14.7 per cent. Effective STI monitoring remains essential for the identification of relevant trends, emerging STIs in high-risk groups, and the effectiveness of prevention programmes. STI clinics offer high-risk groups access to free testing for STI and provide care and treatment if an STI is diagnosed. The total number of consultations in 2013 was 133,585, an increase of 10% compared with 2012. In 2013, STI clinic attendees with an STI were mainly people who reported having been notified of their possible exposure to STI, people aged 20-24, people originating from areas in which STI/HIV is common (e.g. Africa, South America or Eastern Europe), and men who have sex with men (MSM). Chlamydia: With 15,767 cases, chlamydia remains the most commonly diagnosed STI in 2013. The percentage of people diagnosed with chlamydia was slightly lower in 2013 than in 2012 (11.8 versus 12.2 respectively). Chlamydia was primarily diagnosed in heterosexuals younger than 25 years old and in both men and women. Following the increase in the number and percentage of lymphogranuloma venereum (LGV; an aggressive variant of chlamydia) infections in 2012, these numbers declined to a level comparable to previous years in 2013. Gonorrhoea: Whereas the percentage of people with a gonorrhoea infection slightly had increased in previous years, the percentage remained stable in 2013 (3.4 per cent) compared with 2012 (3.6 per cent). Gonorrhoea was mostly diagnosed in MSM. It remains important to monitor the resistance of the gonorrhoea bacteria against the antibiotic currently recommended in the Netherlands, a third-generation cephalosporin. A rising rate of resistance to this antibiotic has been observed in several European countries. HIV:The number of people diagnosed with HIV at STI clinics in 2013 was similar to that of 2012 (358 versus 356 respectively). Among MSM, the percentage of positive HIV tests decreased from 3.0 per cent in 2008 to 1.4 per cent in 2013. The percentage of HIV-positive people who were diagnosed at a late stage of the infection has decreased in previous years. Early diagnosis and treatment of an HIV infection is important because of individual health benefits and the potential reduction of HIV transmission. (aut.ref.