  Policy makers have implemented multiple non-pharmaceutical strategies to
mitigate the COVID-19 worldwide crisis. Interventions had the aim of reducing
close proximity interactions, which drive the spread of the disease. A deeper
knowledge of human physical interactions has revealed necessary, especially in
all settings involving children, whose education and gathering activities
should be preserved. Despite their relevance, almost no data are available on
close proximity contacts among children in schools or other educational
settings during the pandemic. Contact data are usually gathered via Bluetooth,
which nonetheless offers a low temporal and spatial resolution. Recently,
ultra-wideband (UWB) radios emerged as a more accurate alternative that
nonetheless exhibits a significantly higher energy consumption, limiting
in-field studies. In this paper, we leverage a novel approach, embodied by the
Janus system that combines these radios by exploiting their complementary
benefits. The very accurate proximity data gathered in-field by Janus, once
augmented with several metadata, unlocks unprecedented levels of information,
enabling the development of novel multi-level risk analyses. By means of this
technology, we have collected real contact data of children and educators in
three summer camps during summer 2020 in the province of Trento, Italy. The
wide variety of performed daily activities induced multiple individual
behaviors, allowing a rich investigation of social environments from the
contagion risk perspective. We consider risk based on duration and proximity of
contacts and classify interactions according to different risk levels. We can
then evaluate the summer camps' organization, observe the effect of partition
in small groups, or social bubbles, and identify the organized activities that
mitigate the riskier behaviors. [...]
