SARS-CoV-2 transmission patterns in educational settings during the Alpha wave in Reggio-Emilia, Italy
Carla Molina Grané,
Pamela Mancuso,
Massimo Vicentini,
Francesco Venturelli,
Olivera Djuric,
Mattia Manica,
Giorgio Guzzetta,
Valentina Marziano,
Agnese Zardini,
Valeria d’Andrea,
Filippo Trentini,
Eufemia Bisaccia,
Elisabetta Larosa,
Silvia Cilloni,
Maria Teresa Cassinadri,
Patrizio Pezzotti,
Marco Ajelli,
Paolo Giorgi Rossi,
Stefano Merler,
Piero Poletti
Affiliations
Carla Molina Grané
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy; Department of Mathematics, University of Trento, Trento, Italy
Pamela Mancuso
Epidemiology Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Massimo Vicentini
Epidemiology Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Francesco Venturelli
Epidemiology Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Olivera Djuric
Epidemiology Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy; Department of Biomedical, Metabolic and Neural Sciences, Centre for Environmental, Nutritional and Genetic Epidemiology (CREAGEN), Public Health Unit, University of Modena and Reggio Emilia, Reggio Emilia, Italy
Mattia Manica
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy
Giorgio Guzzetta
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy
Valentina Marziano
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy
Agnese Zardini
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy
Valeria d’Andrea
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy
Filippo Trentini
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy; Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy
Eufemia Bisaccia
Public Health Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Elisabetta Larosa
Public Health Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Silvia Cilloni
Public Health Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Maria Teresa Cassinadri
Public Health Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Patrizio Pezzotti
Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
Marco Ajelli
Laboratory for Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA
Paolo Giorgi Rossi
Epidemiology Unit, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
Stefano Merler
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy
Piero Poletti
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy; Corresponding author.
Different monitoring and control policies have been implemented in schools to minimize the spread of SARS-CoV-2. Transmission in schools has been hard to quantify due to the large proportion of asymptomatic carriers in young individuals. We applied a Bayesian approach to reconstruct the transmission chains between 284 SARS-CoV-2 infections ascertained during 87 school outbreak investigations conducted between March and April 2021 in Italy. Under the policy of reactive quarantines, we found that 42.5% (95%CrI: 29.5–54.3%) of infections among school attendees were caused by school contacts. The mean number of secondary cases infected at school by a positive individual during in-person education was estimated to be 0.33 (95%CrI: 0.23–0.43), with marked heterogeneity across individuals. Specifically, we estimated that only 26.0% (95%CrI: 17.6–34.1%) of students and school personnel who tested positive during in-person education caused at least one secondary infection at school. Positive individuals who attended school for at least 6 days before being isolated or quarantined infected on average 0.49 (95%CrI: 0.14–0.83) secondary cases. Our findings provide quantitative insights on the contribution of school transmission to the spread of SARS-CoV-2 in young individuals. Identifying positive cases within 5 days after exposure to their infector could reduce onward transmission at school by at least 30%.
