Innovation in wastewater near-source tracking for rapid identification of COVID-19 in schools
Authors: Francis Hassard, Lian Lundy, Andrew C Singer, Jasmine Grimsley, Mariachiara Di Cesare
Journal: The Lancet Microbe (2020)

COVID-19 is one of the biggest global public health challenges of the century with almost 42 million cases and more than a million deaths to date. Until a COVID-19 vaccine or effective pharmaceutical intervention is developed, alternative tools for the rapid identification, containment, and mitigation of the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are of paramount importance for managing community transmission. Within this context, school closure has been one of the strategies implemented to reduce spread at local and national levels. Experience gained from influenza epidemics showed that school closures reduce social contacts between students and therefore interrupt chains of transmission between students and households.1Jackson C Mangtani P Hawker J Olowokure B Vynnycky E The effects of school closures on influenza outbreaks and pandemics: systematic review of simulation studies.PLoS One. 2014; 9e97297Crossref PubMed Scopus (106) Google Scholar How school-age children transmit coronaviruses such as severe acute respiratory syndrome, Middle East respiratory syndrome, and SARS-CoV-2 within school settings and at a local community scale is less clear. Regardless, as of mid-March 2020, about half the world's student population were required to stay at home. Evidence from human influenza outbreaks (where children are key vectors) indicates that school closures are only effective during low viral transmissivity (defined as reproductive number <2) if viral susceptibility is greater in children than in adults.2Viner RM Russell SJ Croker H et al.School closure and management practices during coronavirus outbreaks including COVID-19: a rapid systematic review.Lancet Child Adolesc Health. 2020; 4: 397-404Summary Full Text Full Text PDF PubMed Scopus (1201) Google Scholar Although the role of children in COVID-19 transmission remains unclear (in terms of both incubation length and asymptomatic prevalence), one report suggested that children and young adults (10–19 years) spread COVID-19 to the same extent as adults,3Park YJ Choe YJ Park O et al.Contact tracing during coronavirus disease outbreak, South Korea, 2020.Emerg Infect Dis. 2020; 26: 2465-2468Crossref PubMed Google Scholar and therefore, can be a source of SARS-CoV-2 in household transmission clusters. However, data is not consistent with earlier studies reporting little evidence of transmission from children to adults.4Zhu Y Bloxham CJ Hulme KD et al.Children are unlikely to have been the primary source of household SARS-CoV-2 infections.medRxiv. 2020; (published online March 30.) (preprint)https://doi.org/10.1101/2020.03.26.20044826Google Scholar This knowledge gap is partly due to disproportionately low rates of community testing on children and adolescents. Surveillance for COVID-19 focuses on identifying and testing individuals with symptoms, an approach that does not capture asymptomatic (40–56% of confirmed SARS-CoV-2 infections5Lavezzo E Franchin E Ciavarella C et al.Suppression of a SARS-CoV-2 outbreak in the Italian municipality of Vo'.Nature. 2020; 584: 425-429Crossref PubMed Scopus (607) Google Scholar) or presymptomatic individuals. Although mass screening is increasingly considered a way to address this problem, costs, equipment availability, and implementation compromise the feasibility of this approach. A promising, non-invasive tool that can support the COVID-19 response is the use of wastewater-based epidemiology to enable the early identification of local outbreaks and facilitate targeted use of local clinical testing.6Polo D Quintela-Baluja M et al.Making waves: wastewater-based epidemiology for COVID-19—approaches and challenges for surveillance and prediction.Water Res. 2020; 186116404Crossref PubMed Scopus (172) Google Scholar SARS-CoV-2 has been identified in adult and child faeces and urine, in asymptomatic individuals and at the presymptomatic stage, with long-lasting virus shedding in the excreta at the convalescent stage in both adults and children.7Jones DL Baluja MQ Graham DW et al.Shedding of SARS-CoV-2 in feces and urine and its potential role in person-to-person transmission and the environment-based spread of COVID-19.Sci Total Environ. 2020; 749141364Crossref PubMed Scopus (213) Google Scholar However, few data are available on the levels and duration of shedding by children not requiring hospital treatment.8Wölfel R Corman VM Guggemos W et al.Virological assessment of hospitalized patients with COVID-2019.Nature. 2020; 581: 465-469Crossref PubMed Scopus (4463) Google Scholar SARS-CoV-2 RNA fragments have been isolated from numerous wastewater treatment works, septic tanks, sewers, hospital wastewater treatment systems, and environmental discharge points7Jones DL Baluja MQ Graham DW et al.Shedding of SARS-CoV-2 in feces and urine and its potential role in person-to-person transmission and the environment-based spread of COVID-19.Sci Total Environ. 2020; 749141364Crossref PubMed Scopus (213) Google Scholar and reported to predate the clinical diagnosis of cases,9Chavarria-Miró G Anfruns-Estrada E Guix S et al.Sentinel surveillance of SARS-CoV-2 in wastewater anticipates the occurrence of COVID-19 cases.medRxiv. 2020; (published online June 13.) (preprint)https://doi.org/10.1101/2020.06.13.20129627Google Scholar, 10Medema G Heijnen L Elsinga G Italiaander R Brouwer A Presence of SARS-coronavirus-2 RNA in sewage and correlation with reported COVID-19 prevalence in the early stage of the epidemic in the Netherlands.Environ Sci Technol Lett. 2020; 7: 511-516Crossref PubMed Scopus (885) Google Scholar raising the potential for its use within an early warning system. Data at a local community level have the potential to proactively inform public health-care strategies (targeting resources with associated time and cost savings) and mitigate escalating demands on health-care providers, especially during the winter months. However, monitoring occurrence or prevalence at the inlet of a wastewater treatment plant does not allow the identification of specific groups of the population, limiting its epidemiological value for managing COVID-19 and breaking chains of transmission. More recently, the wastewater-based epidemiology approach has been successfully used for near-source tracking (NST)—eg, in the sewage drains serving buildings—permitting detection of small clusters or even individual COVID-19 cases. NST, used in combination with targeted clinical testing, has clear potential to stop outbreaks and is now being used across Estonia, Finland, France, Singapore, Turkey, the UK, and the USA. NST might be more easily justified for the more vulnerable or higher risk and undersampled groups such as people in hospitals, prisons, elderly care homes, schools (particularly boarding schools), preschool settings, and factories. Although wastewater-based epidemiology cannot replace clinical testing, routine wastewater surveillance across spatial scales (from sewershed to building to sub-building level) could enable the early identification of local outbreaks through informing the targeted use of local clinical testing (ie, when and where) to capture asymptomatic and presymptomatic cases. Experience from the past month in most of the countries in which the school year has restarted is that as community cases rise, more children become infected. Wastewater-based epidemiology using NST provides public health officials insight into the carriage of COVID-19 within discrete groups of people for whom rapid action could alleviate the risk of a much larger outbreak. Wastewater NST could be the first line of defence for high-risk populations and could offer long-term advances in public health surveillance after COVID-19. We declare no competing interests.