Ziv Shkedy
Catholic University of Leuven
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Publication
Featured researches published by Ziv Shkedy.
BMC Infectious Diseases | 2009
Niel Hens; Nele Goeyvaerts; Marc Aerts; Ziv Shkedy; Pierre Van Damme; Philippe Beutels
BackgroundUntil recently, mathematical models of person to person infectious diseases transmission had to make assumptions on transmissions enabled by personal contacts by estimating the so-called WAIFW-matrix. In order to better inform such estimates, a population based contact survey has been carried out in Belgium over the period March-May 2006. In contrast to other European surveys conducted simultaneously, each respondent recorded contacts over two days. Special attention was given to holiday periods, and respondents with large numbers of professional contacts.MethodsParticipants kept a paper diary with information on their contacts over two different days. A contact was defined as a two-way conversation of at least three words in each others proximity. The contact information included the age of the contact, gender, location, duration, frequency, and whether or not touching was involved.For data analysis, we used association rules and classification trees. Weighted generalized estimating equations were used to analyze contact frequency while accounting for the correlation between contacts reported on the two different days.A contact surface, expressing the average number of contacts between persons of different ages was obtained by a bivariate smoothing approach and the relation to the so-called next-generation matrix was established.ResultsPeople mostly mixed with people of similar age, or with their offspring, their parents and their grandparents. By imputing professional contacts, the average number of daily contacts increased from 11.84 to 15.70. The number of reported contacts depended heavily on the household size, class size for children and number of professional contacts for adults. Adults living with children had on average 2 daily contacts more than adults living without children. In the holiday period, the daily contact frequency for children and adolescents decreased with about 19% while a similar observation is made for adults in the weekend. These findings can be used to estimate the impact of school closure.ConclusionWe conducted a diary based contact survey in Belgium to gain insights in social interactions relevant to the spread of infectious diseases. The resulting contact patterns are useful to improve estimating crucial parameters for infectious disease transmission models.
Journal of Applied Statistics | 2011
An Creemers; Marc Aerts; Niel Hens; Ziv Shkedy; Frank De Smet; Philippe Beutels
We aimed to study the excess health-care expenditures for persons with a known positive isolate of Streptococcus pneumoniae. The data set was compiled by linking the database of the largest Belgian Sickness Fund with data obtained from laboratories reporting pneumococcal isolates. We analyzed the age-specific per-patient cumulative costs over time, using generalized estimating equations (GEEs). The mean structure was described by fractional polynomials. The quasi-likelihood under the independence model criterion was used to compare different correlation structures. We show for all age groups that the health-care costs incurred by diagnosed pneumococcal patients are significantly larger than those incurred by undiagnosed matched persons. This is not only the case at the time of diagnosis but also long before and after the time of diagnosis. These findings can be informative for the current debate on unrelated costs in health economic evaluation, and GEEs could be used to estimate these costs for other diseases. Finally, these results can be used to inform policy on the expected budget impact of preventing pneumococcal infections.
Archive | 2009
Dan Lin; Ziv Shkedy; Tomasz Burzykowski; Dani Yekutieli; A. De Bondt; Whh. Göhlmann; Willem Talloen; Luc Bijnens
Archive | 2018
Marijke Van Moerbeke; Adetayo Kasim; Ziv Shkedy
Archive | 2018
Marijke Van Moerbeke; Adetayo Kasim; Ziv Shkedy
Archive | 2015
Theophile Bigirumurame; Nolen Joy Perualila; Ziv Shkedy; Adetayo Kasim
Archive | 2014
Theophile Bigirumurame; Nolen Joy Perualila; Ziv Shkedy; Adetayo Kasim
Archive | 2013
Pushpike Jayantha Thilakarathne; Ziv Shkedy; Martin Otava; Willem Talloen; Luc Bijnens; Adetayo Kasim
Archive | 2013
Theophile Bigirumurame; Ziv Shkedy; Tomasz Burzykowski; Suzy Van Sanden; Pushpike Jayantha Thilakarathne; Joris Dries
Archive | 2010
Marc Aerts; Geert Molenberghs; Tomasz Burzykowski; Ziv Shkedy; Jef Vanvoorden