Wastewater as a back door to serology?

Wastewater surveillance is a powerful tool for monitoring the prevalence of infectious disease in urban populations, with predictive value for upcoming increases in cases and hospitalizations. The approach primarily used in disease surveillance has been to measure the number of viral copies detected in wastewater for a study area of known population, and systems for wastewater monitoring have been put in place worldwide during the SARS-CoV-2 pandemic. However, the potential to measure other biomarkers such as proteins and metabolites in wastewater has not been fully explored. Here we develop an approach to determine antibody optical density and titer measurements from wastewater. We measured abundance of anti-SARS-CoV-2 spike IgG and IgA from typical fresh samples of community wastewater, and from a collection of frozen samples dating from 2020-22. The assay described can be performed with readily available commercial reagents, at a moderate per-sample cost, facilitating non-invasive population level immune surveillance. Our findings demonstrate the feasibility of indirect serological surveillance through wastewater for population level monitoring, and the protocol described will enable the collection of larger data sets and development of models that can be leveraged to anticipate public health needs. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Funding was provided by the UNC-Charlotte Division of Research. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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 and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data produced and protocols used in the present study are included in full in the article. Authors will respond to any reasonable request for clarification or further information.