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. 2022 Oct 6;14(10):2199.
doi: 10.3390/v14102199.

SARS-CoV-2 Transmission in Belgian French-Speaking Primary Schools: An Epidemiological Pilot Study

Julie Frère  1 , Olga Chatzis  2 , Kelly Cremer  3 , Joanna Merckx  4 , Mathilde De Keukeleire  3 , Florence Renard  5 , Nathalie Ribesse  5 , Frédéric Minner  6 , Jean Ruelle  7   8 , Benoit Kabamba  3   7 , Hector Rodriguez-Villalobos  3   9 , Bertrand Bearzatto  10 , Marie-Luce Delforge  11 , Coralie Henin  12 , Fabrice Bureau  6 , Laurent Gillet  6 , Annie Robert  3 , Dimitri Van der Linden  2
Affiliations

SARS-CoV-2 Transmission in Belgian French-Speaking Primary Schools: An Epidemiological Pilot Study

Julie Frère et al. Viruses. .

Abstract

Schools have been a point of attention during the pandemic, and their closure one of the mitigating measures taken. A better understanding of the dynamics of the transmission of SARS-CoV-2 in elementary education is essential to advise decisionmakers. We conducted an uncontrolled non-interventional prospective study in Belgian French-speaking schools to describe the role of attending asymptomatic children and school staff in the spread of COVID-19 and to estimate the transmission to others. Each participant from selected schools was tested for SARS-CoV-2 using a polymerase chain reaction (PCR) analysis on saliva sample, on a weekly basis, during six consecutive visits. In accordance with recommendations in force at the time, symptomatic individuals were excluded from school, but per the study protocol, being that participants were blinded to PCR results, asymptomatic participants were maintained at school. Among 11 selected schools, 932 pupils and 242 school staff were included between January and May 2021. Overall, 6449 saliva samples were collected, of which 44 came back positive. Most positive samples came from isolated cases. We observed that asymptomatic positive children remaining at school did not lead to increasing numbers of cases or clusters. However, we conducted our study during a period of low prevalence in Belgium. It would be interesting to conduct the same analysis during a high prevalence period.

Keywords: COVID-19; SARS-CoV-2; children; saliva testing; schools; transmission.

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Conflict of interest statement

J.F., O.C., K.C., M.D.K., N.R., F.R., J.R., B.K., H.R.-V., B.B., M.L.D., C.H., A.R. and D.V.d.L. have no conflicts of interest to declare for this study. J.R. became an employee of SmartGene during the course of study data analysis, a company active in bioinformatics services. J.M. was an employee of bioMerieux Canada, Inc until July 2021; this is unrelated to the study. L.G. and F.B. participated in the creation of the saliva collection kit. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Fourteen-day incidence of COVID-19 cases per 100,000 persons by age group and for the general population, from 1 September 2020 to 30 June 2021, Belgium. The incidence is represented by the sum of the number of cases in the previous 14 days over the number of people in that age group. “BE” indicates the whole population in Belgium (all age groups). Shaded areas indicate school holiday periods.
Figure 2
Figure 2
Geographical distribution of primary schools included in the study.
Figure 3
Figure 3
Study flowchart.
Figure 4
Figure 4
Study timeline. Sequentially inclusion of schools in the study. The weeks mentioned correspond to the calendar weeks of the year 2021. Shaded areas indicate the weeks of school visits. School n°5 was closed (optional school holiday) on the day of the study staff’s visit in week 3.
Figure 5
Figure 5
Reported cases of positive SARS-CoV-2 PCR during the study period detected by the study samples and reported by health promotion department from each school. SARS-CoV-2 cases detected by the study DynaTracs (first line) and reported by the school health promotion department (second line). Distinction was made between pupils (p) and adults school staff (SS). The weeks mentioned correspond to the calendar weeks of the year 2021. Shaded areas indicate the weeks of school visits. * School holidays, ** School Interruption for sanitary reasons, *** Return to school. p: pupils, SS: school staff, SHPD: school health promotion department.
Figure 6
Figure 6
Phylogenetic tree comparing reference strains including Wuhan strain and strains from 10 participants. The upper part of the diagram represents the results from reference strains. The shaded part of the diagram represents results from the study samples. * Two strains with similarities, - participants coming from different schools.
See this image and copyright information in PMC

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