Multi-scale wastewater surveillance at a Bangkok tertiary care hospital: A potential sentinel site for real-time COVID-19 surveillance at hospital and national levels.

Wastewater-based epidemiology is a valuable tool for population-level pathogen surveillance, complementing clinical methods. While most sampling focuses on municipal wastewater treatment plants, emerging evidence suggests wastewater collected from hospital settings can lead to targeted clinical interventions. To investigate wastewater pathogen surveillance in hospital settings further, we tracked the presence and concentration of SARS-CoV-2 RNA in wastewater across multi-scale sample sites within a large, public tertiary care hospital in Bangkok, Thailand. From July 2022 to May 2023, weekly wastewater samples (n=392) were collected from various sample sites including clinical and non-clinical facilities, as well as the hospital's wastewater treatment plant. Influent wastewater at the hospital's wastewater treatment center yielded the most consistent SARS-CoV-2 RNA detection across all sample sites, with detection in all 26 samples. Despite varied building usage patterns, significant moderate negative correlations were found in 90% (9/10) of sample sites between wastewater RT-PCR cycle threshold values and clinical case data from hospital and national reports. Targeting specific buildings yielded distinct data trends, indicating their potential to offer complementary insights into viral shedding and transmission among clinical and non-clinical sub-populations within a hospital campus. Our findings suggest that hospital wastewater-based epidemiology reflects broader community disease trends, which may be especially useful in regions with limited municipal wastewater treatment coverage. Large tertiary care hospitals could serve as effective and cost-efficient sentinel surveillance sites for future pathogen monitoring, guiding public health actions.