  Little quantitative information is available on the mixing patterns of
children in school environments. Describing and understanding contacts between
children at school would help quantify the transmission opportunities of
respiratory infections and identify situations within schools where the risk of
transmission is higher. We report on measurements carried out in a French
school (6-12 years children), where we collected data on the time-resolved
face-to-face proximity of children and teachers using a proximity-sensing
infrastructure based on radio frequency identification devices.
  Data on face-to-face interactions were collected on October 1st and 2nd,
2009. We recorded 77,602 contact events between 242 individuals. Each child has
on average 323 contacts per day with 47 other children, leading to an average
daily interaction time of 176 minutes. Most contacts are brief, but long
contacts are also observed. Contacts occur mostly within each class, and each
child spends on average three times more time in contact with classmates than
with children of other classes. We describe the temporal evolution of the
contact network and the trajectories followed by the children in the school,
which constrain the contact patterns. We determine an exposure matrix aimed at
informing mathematical models. This matrix exhibits a class and age structure
which is very different from the homogeneous mixing hypothesis.
  The observed properties of the contact patterns between school children are
relevant for modeling the propagation of diseases and for evaluating control
measures. We discuss public health implications related to the management of
schools in case of epidemics and pandemics. Our results can help define a
prioritization of control measures based on preventive measures, case
isolation, classes and school closures, that could reduce the disruption to
education during epidemics.
