1,721,107 research outputs found
Population dynamics of endemic mosquito species and their epidemiological implications in Northern Italy
No full textThe rapid invasion and spread of Aedes albopictus within new continents and climatic ranges has created favorable conditions for the emergence of tropical arboviral diseases in the invaded areas. We used mosquito abundance data from 2014 and 2015 collected across ten sites in northern Italy to calibrate a population model for Ae. albopictus and to estimate the transmission potential of chikungunya, dengue and ZIKV. The model predicts a significant risk of chikungunya outbreaks in most sites if a case is imported between the beginning of summer and up to mid-November, with an average outbreak probability between 4.9% and 25%. Peak values of R0 range from 0.5 to 3 depending on the site. A lower risk is predicted for dengue, with an average probability between 4.2% and 10.8% for cases imported between mid-July and mid-September and peak values of R0 from 0.5 to 2. Importantly, R0 of dengue remains above the epidemic threshold for a much shorter period of time. We estimated the basic reproductive number R0for ZIKV to be systematically below the epidemic threshold in most scenarios. The main determinants of transmissibility are i) local abundance of Ae. albopictus, which in turn depends on local temperature patterns, precipitation – a robust negative correlation was found with late spring precipitations – and habitat suitability, and ii) natural history of the diseases. In particular, the lower estimated risk for dengue is mainly determined by the length of the extrinsic incubation period in Ae. albopictus, while the lower risk of ZIKV is mainly ascribable to the low transmission efficiency of Ae. albopictus, compared for instance to that of Ae. aegypti
Model predictions and evaluation of possible control strategies for the 2009 A/H1N1v influenza pandemic in Italy RID E-1905-2011
No full textEvaluation of model prediction during the early phase of the 2009 influenza pandemic in Italy
No full textDuring the early phases of the 2009 influenza pandemic in Italy, real-time modeling analysis were conducted in order to estimate the impact of the pandemic. In order to evaluate the results obtained by the model we compared simulated epidemics to the estimated number of influenza-like illness (ILI) collected by the Italian sentinel surveillance system (INFLUNET), showing a good agreement with the timing of the observed epidemic. By assuming in the model mitigation measures implemented in Italy, the peak was expected on week 44 (95% CI: 44, 45). Results were consistent with the INFLUNET data showing that the peak in Italy was reached in week 46. These predictions have proved to be a valuable support for public health policy makers for planning interventions for mitigating the spread of the pandemic
The role of climatic factors in shaping mosquito population dynamics: the case of Culex pipiens in Northwestern Italy
No full textCulex pipiens mosquito is a species widely spread across Europe and represents a competent vector for many human diseases such as West Nile virus (WNV), which has been circulating in many European countries during last years, causing hundreds of human cases. Rigorous surveillance of mosquito density and control programs based on the reduction of the mosquito population represent key components of disease containment and prevention. Therefore, in order to design appropriate control strategies it is crucial to investigate the influence of climatic factors on the dynamics of vector populations during a typical breeding season.
To understand which are the main determinants of the high heterogeneity observed in Piedmont region (Northwestern Italy) in Culex pipiens abundance across different seasons, we developed a density dependent mathematical model that takes explicitly into account the mechanisms of diapause characterizing the overwintering of adult mosquitoes (driven by the daylight duration), and the role played by temperature, which strongly affects both developmental and death rates of different life stages of Culex pipiens. The model was calibrated by performing a Bayesian statistical analysis of weekly capture data gathered in our study site from 2000 to 2011.
Our analysis suggests that the high heterogeneity characterizing the dynamics of mosquito density among different years is driven by differences in the temporal patterns of temperature and in the larval carrying capacity associated to different breeding seasons. Specifically, high temperatures during early spring may anticipate the onset of the breeding season, while higher temperatures during late spring are associated with longer seasons. On the opposite, high temperatures during the summer can reduce the Culex pipiens abundance by increasing the adult mortality during this period.
Our results show that higher density of adult mosquitoes are associated to higher larval carrying capacities which result positively correlated with spring precipitations suggesting that more rain during spring can create more breeding sites.
Finally, our simulations show that the initial number of adults does not affect the vector abundance of a specific season, suggesting that two consecutive years might be unrelated and that the inter-seasonal heterogeneity might not be influenced by the adults’ ability of overwintering
Geographical information systems and bootstrap aggregation (bagging) of tree-based classifiers for lyme disease risk prediction in Trentino, Italian Alps
No full textThe risk of exposure to Lyme disease in the province of Trento, Italian Alps, was predicted through the analysis of the distribution of Ixodes ricinus (L.) nymphs infected with Borrelia burgdorferi s.l. with a model based on bootstrap aggregation (bagging) of tree-based classifiers within a geographical information system (GIS). Data on I. ricinus density assessed by dragging the vegetation in 438 sites during 1996 were cross-correlated with the digital cartography of a GIS, which included the variables altitude, exposure and slope, substratum, vegetation type and roe deer density. Ticks were more abundant at altitudes below 1,300 m a.s.l., in the presence of limestone and vegetation cover with thermophile deciduous forests and high densities of roe deer. A bootstrap aggregation procedure (bagging) was used to produce a model for the prediction of tick occurrence, the accuracy of which was tested on actual tick counts assessed by a further dragging campaign carried out during 1997 to determine infection prevalence and resulted in average 77%. Other tests of the model were made on additional and independent data sets. The prevalence of infection with Borrelia burgdorferi s.l, determined by polymerase chain reaction on 2,208 nymphs collected by random dragging in 245 transects selected within eight areas where the model predicted the occurrence of I. ricinus during 1997, was 17.5% and was positively correlated to tick abundance and roe deer density. These findings were used to relate the output of the bagged model (probability of tick occurrence) to the density of infected nymphs through a stepwise model selection procedure and thus to produce a GIS digital map of the probability distribution of infected nymphs in the Province of Trento at high resolution scale (50 by 50-m cell resolution). The application of the bagging procedure increased the accuracy of the prediction made by a single classification tree, a well-known classification method for the analysis of epidemiological dat
Estimating measles transmission potential in Italy over the period 2010-2011
No full textBackground. Recent history of measles epidemiology in Italy is characterized by the recurrence of spatially localized epidemics. Aim. In this study we investigate the three major outbreaks occurred in Italy over the period 2010-2011 and estimate the measles transmission potential. The epidemics mainly involved individuals aged 10-28 years and the transmission potential, measured as effective reproduction number i.e. the number of new infections generated by a primary infector - was estimated to be 1.9-5.9. Results. Despite such high values, we found that, in all investigated outbreaks, the reproduction number has remained above the epidemic threshold for no more than twelve weeks, suggesting that measles may hardly have the potential to give rise to new nationwide epidemics. Conclusion. In conclusion, the performed analysis highlights the need of planning additional vaccination programs targeting those age classes currently showing a higher susceptibility to infection, in order not to compromise the elimination goal by 2015
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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