Wastewater-based surveillance of respiratory syncytial virus epidemic at the national level in Finland

The purpose of this study was to evaluate the potential of wastewater-based surveillance in the monitoring of epidemics at the national level in Finland. To discover the correlation of wastewater data and register data, the 2021–2022 respiratory syncytial virus (RSV) epidemic in Finland was analyzed from wastewater and the Finnish National Infectious Diseases Register. The study was performed using samples that were collected monthly from May 2021 to July 2022 from ten wastewater treatment plants that cover 40% of the Finnish population. Respiratory syncytial virus detection in 24-h composite samples of influent wastewater was performed using RT-qPCR. Respiratory syncytial virus wastewater data were positively correlated with the National Infectious Diseases Register data for the sampling week (correlation coefficient, CC min = 0.412, max = 0.865). Furthermore, the cumulative incidence of respiratory syncytial virus from the sampling week to three weeks afterward was strongly correlated with the wastewater data (CC min = 0.482, max = 0.814), showing the potential of wastewater-based surveillance for use in estimating the course of the epidemic. When the register-based incidence of RSV was at least four cases/100,000 persons/week in the sampling week, it was detected in all wastewater samples. This study showed that wastewater surveillance is useful in the surveillance of respiratory syncytial virus epidemics, and its potential in the surveillance of other epidemics should be explored further. Synopsis Environmental surveillance has been previously used to monitor viruses such as poliovirus and SARS-CoV-2. This study shows that wastewater-based surveillance can be used to surveil the respiratory syncytial virus and its epidemics, at a national level. ### Competing Interest Statement Sami Oikarinen reports a relationship with Greenseq Ltd that includes: board membership. Kirsi-Maarit Lehto reports a relationship with Greenseq Ltd that includes: board membership and travel reimbursement. ### Funding Statement This work was funded by Academy of Finland, grant number 339416. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The clinical RSV data was retrieved from the Finnish National Infectious Diseases register: . The Finnish Institute for Health and Welfare took part in this study and granted permission to use the data. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors * ### Abbreviations RSV : Respiratory syncytial virus NIDR : National Infectious Diseases Register WWTP : Wastewater treatment plant WBS : Wastewater-based surveillance RT-qPCR : Reverse-transcription quantitative polymerase chain reaction