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Students attending schools play an important role in the transmission of influenza. In this study, we present a social network analysis of contacts among 1,828 students in eight different schools in urban and suburban areas in and near Pittsburgh, Pennsylvania, United States of America, including elementary, elementary-middle, middle, and high schools. We collected social contact information of students who wore wireless sensor devices that regularly recorded other devices if they are within a distance of 3 meters. We analyzed these networks to identify patterns of proximal student interactions in different classes and grades, to describe community structure within the schools, and to assess the impact of the physical environment of schools on proximal contacts. In the elementary and middle schools, we observed a high number of intra-grade and intra-classroom contacts and a relatively low number of inter-grade contacts. However, in high schools, contact networks were well connected and mixed across grades. High modularity of lower grades suggests that assumptions of homogeneous mixing in epidemic models may be inappropriate; whereas lower modularity in high schools suggests that homogenous mixing assumptions may be more acceptable in these settings. The results suggest that interventions targeting subsets of classrooms may work better in elementary schools than high schools. Our work presents quantitative measures of age-specific, school-based contacts that can be used as the basis for constructing models of the transmission of infections in schools.

The effect of school-based non-pharmaceutical interventions (NPIs) on influenza A and B transmission in children's households has not been estimated in published literature. We use data from a large school-based cluster randomized trial of improved hand and respiratory hygiene measures to explore the secondary transmission of influenza A and B in households of laboratory confirmed influenza cases. Data were taken from the Pittsburgh Influenza Prevention Project, a cluster-randomized trial of NPIs conducted in ten Pittsburgh, PA elementary schools during the 2007-2008 influenza season. We estimated two measures of influenza transmissibility in households; the susceptible infectious transmission probability, using variants of the Reed-Frost chain binomial model, and the secondary attack rate. We identified predictors of ILI using a logistic generalized estimating equation model. We estimate the secondary attack rates in intervention households to be 0.26 (95% confidence interval (CI) 0.19-0.34) compared to 0.30 (95% CI 0.23-0.38) in control households. Race and age were significant risk factors for secondary ILI acquisition in this study. We found no significant differences between the transmission probabilities for infectious individuals in intervention (0.19, 95% CI 0.14-0.25), and control households (0.22, 95% CI 0.16-0.29). Similarly, estimates for secondary attack rates and transmission probabilities for households with confirmed influenza A (0.31 and 0.22) were not significantly different from estimates from households with confirmed influenza B (0.25 and 0.20). While influenza A and B are thought to have different transmission characteristics, we find no significant differences in their transmissibility within households. Though our results suggest a potential effect, we found no statistically significant effect of school-based non-pharmaceutical interventions on transmission in symptomatic children's homes., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Objectives: The Pittsburgh Influenza Prevention Project (PIPP) has previously shown that school-aged children in grades K-5 can learn hygiene-based, nonpharmaceutical interventions (NPIs) and persist in these behaviors over the duration of an influenza season. The purpose of this study was to determine whether age (as estimated by grade) plays any role in this ability., Methods: The Pittsburgh Influenza Prevention Project is a prospective, controlled, randomized trial of the effectiveness of a suite of NPIs in 10 elementary schools. The project measured adoption of NPIs by students through surveys of intervention homeroom teachers before, during, and after the influenza season and control home-room teachers after influenza season., Results: There were large, statistically significant improvements and persistence over time across all grade levels, in students' concern about influenza and their daily practice of NPIs that promote health behaviors-"wash or sanitize your hands often" and "cover your coughs and sneezes." Nonpharmaceutical interventions characterized as extinguishing unhealthy behaviors, such as "avoid touching your eyes, nose, and mouth" or "home is where you stay when you are sick," showed no reliable improvement., Conclusions: The study provides evidence that elementary school-aged children, across all grades, can understand and implement protective NPIs and maintain these activities throughout influenza season and beyond. Improvements were most prominent when teaching students to engage in health-promoting behaviors. Habitual behaviors (unconscious touching) and changing family behaviors (staying home) seem less susceptible to intervention. These results will be useful to public health policy makers and health care practitioners considering methods of infectious disease prevention in school-based settings.