Varicella-Zoster Virus in Perth, Western Australia: Seasonality and Reactivation.

Identification of the factors affecting reactivation of varicella-zoster virus (VZV) largely remains an open question. Exposure to solar ultra violet (UV) radiation is speculated to facilitate reactivation. Should the role of UV in reactivation be significant, VZV reactivation patterns would generally be expected to be synchronous with seasonal UV profiles in temperate climates.We analysed age and gender specific VZV notification time series data from Perth, Western Australia (WA). This city has more daily sunshine hours than any other major Australian city. Using the cosinor and generalized linear models, we tested these data for seasonality and correlation with UV and temperature.We established significant seasonality of varicella notifications and showed that while herpes-zoster (HZ) was not seasonal it had a more stable seasonal component in males over 60 than in any other subpopulation tested. We also detected significant association between HZ notifications and UV for the entire Perth population as well as for females and males separately. In most cases, temperature proved to be a significant factor as well.Our findings suggest that UV radiation may be important for VZV reactivation, under the assumption that notification data represent an acceptably accurate qualitative measure of true VZV incidence

Monthly HZ notifications in Perth Metropolitan Area by age group (adjusted for variations in size of each group over years).

<p>We only included full years, so the data from the beginning of 2014 to April, 2014 are not shown. The groups are defined as in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151319#pone.0151319.ref014" target="_blank">14</a>].</p

Normalised varicella and HZ notifications for the resident Perth population, maximum UV and temperature averaged by month over the period of January, 2009 to April, 2014.

<p>Normalised varicella and HZ notifications for the resident Perth population, maximum UV and temperature averaged by month over the period of January, 2009 to April, 2014.</p

Non-stationary cosinor model fitted (red) to HZ notifications for Perth (blue).

<p>The fitted line is the mean and the grey area is the 95% confidence interval (both calculated based on 10,000 Markov chain Monte Carlo samples; see [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151319#pone.0151319.ref020" target="_blank">20</a>] for details).</p

Monthly VZV notification rates in Perth Metropolitan Area (adjusted for the size of the at-risk population).

<p>Monthly VZV notification rates in Perth Metropolitan Area (adjusted for the size of the at-risk population).</p

Seasonal component for HZ in the 60+ Perth females (top) and males (bottom).

<p>The grey area is the 95% confidence interval (calculated based on 10,000 Markov chain Monte Carlo samples, see [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151319#pone.0151319.ref020" target="_blank">20</a>] for details).</p

Adaptive Markov chain Monte Carlo forward projection for statistical analysis in epidemic modelling of human papillomavirus

A Bayesian statistical model and estimation methodology based on forward projection adaptive Markov chain Monte Carlo is developed in order to perform the calibration of a high-dimensional nonlinear system of ordinary differential equations representing an epidemic model for human papillomavirus types6 and 11 (HPV-6, HPV-11). The model is compartmental and involves stratification by age, gender and sexual-activity group. Developing this model and a means to calibrate it efficiently is relevant because HPV is a very multi-typed and common sexually transmitted infection with more than 100 types currently known. The two types studied in this paper, types6 and 11, are causing about 90% of anogenital warts.We extend the development of a sexual mixing matrix on the basis of a formulation first suggested by Garnett and Anderson, frequently used to model sexually transmitted infections. In particular, we consider a stochastic mixing matrix framework that allows us to jointly estimate unknown attributes and parameters of the mixing matrix along with the parameters involved in the calibration of the HPV epidemic model. This matrix describes the sexual interactions between members of the population under study and relies on several quantities that are a priori unknown. The Bayesian model developed allows one to estimate jointly the HPV-6 and HPV-11 epidemic model parameters as well as unknown sexual mixing matrix parameters related to assortativity.Finally, we explore the ability of an extension to the class of adaptive Markov chain Monte Carlo algorithms to incorporate a forward projection strategy for the ordinary differential equation state trajectories. Efficient exploration of the Bayesian posterior distribution developed for the ordinary differential equation parameters provides a challenge for any Markov chain sampling methodology, hence the interest in adaptive Markov chain methods. We conclude with simulation studies on synthetic and recent actual data. © 2012 John Wiley & Sons, Ltd.