Teleworking in half-groups reduces contamination, according to a study – LCI

One comes on site, the other stays at home: rotating telework between two groups would be the best strategy to prevent a case of Covid from leading to an epidemic outbreak in a company, a school or a high school, shows a French study published on Thursday, August 26. The authors, from several research organizations including the CNRS, INRIA and the University of Paris, sought to know which measure was the most effective for “stop an epidemic spread in a community from a first positive case”.

The study looked at two distinct devices. First of all, the work-study strategy, which can be favored to maintain cohesion between employees and students, consists of everyone going to the office or to class at the same time, then staying at home at the same time. The rotation divides the group in two: a group A going there while the group B stays at home, before reversing.

For the three places studied (a company, a primary school and a preparatory class in a high school), the result is the same, classified “from best to worst” : “a weekly rotation, a daily rotation, a weekly alternation and a daily alternation”, concludes the study, published in the journal Plos Computational Biology.

This system “hybrid” was set up in part of French colleges and high schools during the previous school year and could make a comeback if the health situation deteriorates, even if for the time being, the start of the school year is scheduled for “face-to-face” for all students, following the implementation of a “level 2” protocol. Distance courses are only planned when one of the students in a group tests positive, according to different modalities between primary and secondary.

The model designed by the researchers simulates the interactions between individuals, but also the “behviour” Sars-CoV-2 virus, with the existence of “superpropagators”, which can infect many more people than average if they are infected, as well as the possibility of being contagious before symptoms appear. In the case of primary school, in the absence of any measure, they estimate that there is more than one risk in four (27.3%) that the positive case will lead to an epidemic focus (defined as in minus five other infected people).

This proportion falls to 17.3% with a daily alternation, 16.6% with a weekly alternation and 12.3% with a weekly rotation, that is to say a risk divided by more than half in the best scenario. The latter technique is the most effective device for extending the time before the first case leads to an epidemic focus and for reducing the total number of infected people, the study estimates.

However, these strategies only work if the circulation of the virus is still limited: in the case of high school, if the local reproduction rate of the virus before taking measurements is greater than 1.7, that is to say that each infected person in the affected area contaminates an average of 1.7 others, “none of these strategies, apart from full-time distancing, is sufficient to prevent the emergence of an epidemic focus”. On the other hand, with a lower reproduction rate, between 1 and 1.38, the four strategies make it possible to lower it even further by bringing it below 1, the threshold below which the epidemic regresses.

Since June 9, employees have been allowed to return to face-to-face work after several months of recommended teleworking, but some companies continue to maintain remote work, which is favored by a majority of French people. According to a survey by the Institut Montaigne published on June 3, 60% of French people would like, “Once the Covid-19 epidemic is over, that companies set up the possibility for employees to telework on part of the working time and be face-to-face on the other part”.