Analysis of mitigation of Covid-19 outbreaks in workplaces and schools by hybrid telecommuting

Mauras, S.; Cohen-Addad, V.; Duboc, G.; Dupre la Tour, M.; Frasca, P.; Mathieu, C.; Opatowski, L.; Viennot, L.

The Covid-19 outbreak has led countries to implement unprecedented measures to limit virus spread within the population, impacting in particular the organization of workplaces, universities, schools. Yet, the power and limitations of such strategies remain unquantified. Here, we develop a simulation study to analyze Covid-19 transmission on three real-life contact networks from a workplace, a primary school and a high school in France, gathered by SocioPatterns, and assess the impact of organization strategies. Investigated strategies include rotations, which consist in partitioning the individuals into two groups, with a presence switch between groups on a weekly or daily frequency ; and On-Off, which consist in keeping everybody together but alternating presence and telecommuting periods. Assuming baseline non pharmaceutical interventions and reactive isolation of symptomatic cases, all strategies where assessed based on a selection of criteria (outbreak probability, outbreak size, and delay before outbreak) and for reproduction numbers ranging 0.5-2. Our results are clear: whatever the network used, the ranking of the strategies based on their ability to mitigate epidemic propagation in the network from a first index case is always the same, namely, from best to worst: Rotation week-by-week, Rotation day-by-day, On-Off week-by-week, and On-Off day-by-day. The advantage of a weekly alternation over a daily alternation, despite significant, is very slight: for the attack rate when there is an outbreak in a high school for example, the numbers for On-Off are 16.8 vs. 18.4 (out of 327 individuals), a 9% improvement. Our results suggest that when the effective reproduction number R within the network is less than 1.34, therefore assuming concurrent implementation of social distancing and other non pharmaceutical interventions, all four strategies efficiently control the outbreak by decreasing effective R to less than 1; the choice between them should therefore be guided by considerations of practical feasibility.