Browsing Articles and other publications by RIVM employees by Title
Now showing items 3819-3838 of 3908
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Waning and boosting: on the dynamics of immune status.The aim is to describe the distribution of immune status (as captured by antibody level) on the basis of a within-host submodel for continuous waning and occasional boosting. Inspired by Feller's fundamental work and the more recent delay equation formulation of models for the dynamics of physiologically structured populations, we derive, for given force of infection, a linear renewal equation. The solution is obtained by generation expansion, with the generation number corresponding to the number of times the individual became infected. Our main result provides a precise characterization of the stable distribution of immune status.
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Weather correlates of Campylobacter prevalence in broilers at slaughter under tropical conditions in Sri Lanka.Campylobacter is the primary agent of human bacterial gastroenteritis worldwide. In contrast to temperate zones, weather effects on Campylobacter prevalence in broilers under tropical conditions are under-researched. We examined the association between weather and Campylobacter prevalence in slaughtered broilers in Sri Lanka, a tropical country with weather variations led by monsoons. Each month (October 2009-July 2011), 20-30 broiler batches referring to two semi-automated slaughterhouses from five Sri Lankan provinces were tested for Campylobacter contamination and analysed in relation to temperature, humidity and rainfall. Overall prevalence was 63.8% (95% CI 59.6-67.9%, n = 542), peaking in September-November. Each 1 °C increase in monthly mean temperature up to 26 °C increased Campylobacter-positive batches by 16.4% (95% CI 0.4-35.1%). For each 10 mm increase in monthly total rainfall up to 300 mm, Campylobacter-positive batches increased significantly by 0.8% (0.1-1.5%) at 1-month lag. For each 1% increase in relative humidity up to 80% at 1- and 2-month lags, Campylobacter-positive batches increased of respectively 4.2% (1.9-6.7%) and 4.0% (1.5-6.5), and decreased by 3.6% (2.6-4.6%) and 4.0% (2.6-5.4%) for unit increases above 80%. These results suggest that even in tropical countries without marked seasons, there are weather effects possibly reflecting Campylobacter potential to colonise its preferred host and/or survive in the environment.
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What benefits and harms are important for a decision about cervical screening? A study of the perspective of different subgroups of women.Background: In cervical screening programs, women typically receive information leaflets to support their decision about participation. However, these leaflets are often based on what experts consider important benefits and harms of screening and not what women themselves consider important to know. Objective: To identify which benefits and harms women consider important for making a decision about cervical screening. Design: Cross-sectional study. Setting and participants: Women from the Dutch target group of cervical screening (N=248; 30-60 years), recruited through an online access panel. Main variables studied: Perceived importance of different benefits and harms of cervical screening, assessed through two rating items ("How important is the information about [this harm/benefit] for your decision?" and "For me it is a [benefit/harm] that participating in the screening program leads to [the benefit/harm]"), and one ranking item ("Rank the information according to their importance for your own choice"). Results: Women overall considered the benefits of cervical screening more important than the harms or disadvantages. The most important harm according to women was the chance of false positive results (M=4.88; SD=1.75). Differences between those with lower and higher numeracy/health literacy were found regarding several aspects, e.g. for the chance of false positive results, the chance of false negative results, the chance of overtreatment. Discussion and conclusion: The results suggest that leaflets could include more explicit information about false positive results.