In schools, masks and air cleaners were associated with stopping COVID-19

Study of two Swiss schools shows the virus spread frequently among students during Omicron wave

Peer-Reviewed Publication

PLOS

 

IMAGE: NEW STUDY FINDS THAT MASKING AND PORTABLE AIR CLEANERS WERE ASSOCIATED WITH REDUCING THE SPREAD OF THE VIRUS THAT CAUSES COVID-19 IN TWO SWISS SCHOOLS. view more 

CREDIT: MARCO FILECCIA, UNSPLASH (CC0, HTTPS://CREATIVECOMMONS.ORG/PUBLICDOMAIN/ZERO/1.0/)

A new study shows that masking and portable air cleaners reduced the spread of the virus that causes COVID-19 in two Swiss schools. A team led by Nicolas Banholzer and Kathrin Zürcher of the University of Bern, Switzerland, publish these findings on May 18th in the open access journal PLOS Medicine.

During the early part of the COVID-19 pandemic, public health authorities worldwide closed schools to prevent the virus’ spread. This decision sparked intense debate over the role of school children in transmission – a risk that is still poorly understood. In the new study, researchers used molecular, environmental and epidemiological data to understand how the virus that causes COVID-19 spread in two secondary schools in Switzerland, from January to March 2022 during the Omicron wave. The study included 90 students and looked at viral transmission in classes with and without masking or air cleaners.

The researchers consistently detected salivary and airborne SARS-CoV-2, the virus that causes COVID-19, in air samples and samples from students throughout the study period. However, concentrations of airborne SARS-CoV-2 were, on average, 70% lower with mask mandates and 40% lower with air cleaners. The findings suggest that between 2 and 19 infections could be avoided while masks were mandated.

The levels of airborne virus detected within the schools indicated that SARS-CoV-2 was continually transmitting among students, and that mask mandates were highly effective at reducing airborne concentrations, thus potentially preventing transmission. The researchers conclude that this monitoring approach could be used during future epidemics of respiratory viral infections to help understand transmission patterns, and whether suggested infection control measures are effective in reducing transmission.

Coauthor Lukas Fenner adds, “Although our study has several limitations, including the observational nature of our study and that detecting SARS-CoV-2 in the air or aerosols does not necessarily mean transmission, we found that mask mandates reduced transmission in classrooms, and both masks and air cleaners reduced aerosol concentrations.”

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In your coverage, please use this URL to provide access to the freely available paper in PLOS Medicine: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1004226

Citation: Banholzer N, Zürcher K, Jent P, Bittel P, Furrer L, Egger M, et al. (2023) SARS-CoV-2 transmission with and without mask wearing or air cleaners in schools in Switzerland: A modeling study of epidemiological, environmental, and molecular data. PLoS Med 20(5): e1004226. https://doi.org/10.1371/journal.pmed.1004226

Author Countries: Switzerland, South Africa, United Kingdom

Funding: see manuscript

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JOURNAL

PLoS Medicine

DOI

10.1371/journal.pmed.1004226 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

COI STATEMENT

Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: ME serves on PLOS Medicine’s editorial board. All authors have declared that no competing interests exist.