具有异质性扩散率的传染病模型分析

为了刻画大尺度空间范围内的个体移动对疾病传播的影响,主要研究了异质集合种群网络的传染病传播过程。由于城市之间存在规模以及交通发达程度等方面的异质性,扩散率也存在一定的异质性。以城市作为节点,建立了具有异质性扩散率的传染病动力学模型,更加准确地刻画了网络结构以及人们的出行对疾病传播的影响。通过对系统进行定性及稳定性分析,发现系统存在一个无病平衡点,并得到了无病平衡点不稳定的阈值条件。当达到疾病爆发的阈值条件时,系统存在唯一的地方病平衡点,并且地方病平衡点是局部渐近稳定的。通过数值模拟验证了理论的正确性。研究表明,增大扩散率能加快疾病的流行速度,因此,通过有效控制大城市的人口出行率可以在一定程度上控制疾病的爆发。     

Vulnerability of motorcycle riders and co-riders to injuries in multi-occupant crashes

In developing countries, most motorcycles are ridden with more than one occupant. The objective of this study was to establish the relative vulnerability of riders and co-riders to injury and determine the injury risk factors in multi-occupant motorcycle crashes. Between January and December 2010, we collected crash and injury data from victims of multi-occupant motorcycle. It is a hospital-based study. The probability of sustaining injuries was similar for co-riders and riders, but co-riders were more likely to sustain severe injuries. Occupants of >2-occupant motorcycles were also more likely to be involved in risky behaviours like not wearing helmet and speeding than those on 2-occupant motorcycles. Occupants of motorcycles on which there were more than two occupants were at an increased risk of sustaining injuries compared with occupants of motorcycles with only two occupants (OR: 2.1, 95% CI: 1.1–4.3). Motorcycle co-riders were more vulnerable to severe injuries than riders. The significance of the study finding to prevention was discussed.     

The cost effectiveness of a quadrivalent human papillomavirus vaccine (6/11/16/18) in Hungary

Abstract

Objective: A transmission dynamic model was used to assess the epidemiological and economic impact of a quadrivalent human papillomavirus (HPV) (6/11/16/18) vaccine in preventing cervical cancer, cervical intraepithelial neoplasia grades 2 and 3 (CIN 2/3), CIN 1 and genital warts in Hungary.

Methods: The routine vaccination of 12-year-old girls and the routine vaccination of 12-year-old girls plus a temporary catch-up programme for girls and women aged 12–24 years was evaluated.

Results: The model projected that at year 100, both strategies could reduce the incidence of HPV 6/11/16/18-related cervical cancer, CIN 2/3, CIN 1 and genital warts cases among Hungarian women by 90%, 90%, 85% and 93%, respectively. Twenty-five years after the introduction of HPV vaccination in the population, routine vaccination of girls by the age of 12 reduced the cumulative number of cases of cervical cancer, CIN 2/3, CIN 1 and genital warts by 685, 13,473, 3,423 and 163,987, respectively. The incremental cost-effectiveness ratios of the two vaccination strategies were €9,577 and €10,646 per quality-adjusted life-year (QALY) gained over a time horizon of 100 years.

Key limitations: The model did not account for the health and economic impact of other HPV diseases which may result from HPV 16, 18, 6, and 11 infections such as vaginal, vulvar, penile, anal and head-neck cancers, and recurrent respiratory papillomatosis. Epidemiological data from Hungary on these other HPV diseases as well genital warts are needed.

Conclusion: A quadrivalent HPV vaccination programme can reduce the incidence of cervical cancer, CIN and genital warts in Hungary at a cost-per-QALY ratio within the range defined as cost effective.     

Epidemiology of yoga-related injuries in Canada from 1991 to 2010: a case series study

The aim is to describe the epidemiology of yoga injuries presenting to select Canadian emergency departments (EDs). Those who presented with a yoga injury to a Canadian ED participating in the Canadian Hospitals Injury Reporting and Prevention Program and had completed a data collection form between 1991 and 2010 were included. Demographic and injury characteristics were tabulated and injury profiles of children were compared to adults. Sixty-six individuals (48 female, 18 male) who sustained 67 injuries were included. The median age was 19 (intraquartile range: 13, 32) and 73% of individuals were injured after 2005 (p = 0.0003). Sprain was the most common injury (23/67, 34%) and the most common body region injured was the lower extremity (27/67, 42%). Significantly more children were injured while being instructed than adults (p = 0.003) but more adults required treatment (p = 0.023). Although yoga-related injuries presenting to an ED are not common, the number of injuries are increasing.     

Bayesian interval estimation for the difference of two independent Poisson rates using data subject to under‐reporting

Comparing occurrence rates of events of interest in science, business, and medicine is an important topic. Because count data are often under‐reported, we desire to account for this error in the response when constructing interval estimators. In this article, we derive a Bayesian interval for the difference of two Poisson rates when counts are potentially under‐reported. The under‐reporting causes a lack of identifiability. Here, we use informative priors to construct a credible interval for the difference of two Poisson rate parameters with under‐reported data. We demonstrate the efficacy of our new interval estimates using a real data example. We also investigate the performance of our newly derived Bayesian approach via simulation and examine the impact of various informative priors on the new interval.