Preprint
en Inglés
| PREPRINT-MEDRXIV | ID: ppmedrxiv-22273861
BackgroundIn fall 2020 when schools in the Netherlands operated under a limited set of COVID-19 measures, we conducted outbreaks studies in four secondary schools to gain insight in the level of schooltransmission and the role of SARS-CoV-2transmission via air and surfaces. MethodsOutbreak studies were performed between 11 November and 15 December 2020 when the wild-type variant of SARS-CoV-2 was dominant. Clusters of SARS-CoV-2 infections within schools were identified through a prospective schoolsurveillance study. All school contacts of cluster cases, irrespective of symptoms, were invited for PCR testing twice within 48 hrs and 4-7 days later. Combined NTS and saliva samples were collected at each time point along with data on recent exposure and symptoms. Surface and active air samples were collected in the schoolenvironment. All samples were PCR-tested and sequenced when possible. ResultsOut of 263 sampled school contacts, 24 tested SARS-CoV-2 positive (secondaryattack rate 9.1%), of which 62% remained asymptomatic and 42% had a weakly positive test result. Phylogenetic analysis on 12 subjects from 2 schools indicated a cluster of 8 and 2 secondary cases, respectively, but also other distinct strains within outbreaks. Of 51 collected air and 53 surface samples, none were SARS-CoV-2 positive. ConclusionOur study confirmed within schoolSARS-CoV-2transmission and substantial silent circulation, but also multiple introductions in some cases. Absence of air or surface contamination suggests environmental contamination is not widespread during schooloutbreaks.