First Wastewater-Based Surveillance of Tomato Brown Rugose Fruit Virus (ToBRFV) in Korea.

Monitoring human fecal contamination in wastewater is crucial for public health and environmental safety. Traditional fecal indicator bacteria (FIB), such as Escherichia coli and Enterococci, lack source specificity between human and non-human sources. Tomato brown rugose fruit virus (ToBRFV) has emerged as a promising viral indicator, characterized by high environmental stability, specificity for human feces, and widespread occurrence in wastewater systems. This study evaluates ToBRFV as a novel RNA-based viral indicator for wastewater surveillance in Korea. Wastewater samples were collected from six wastewater treatment plants (WWTPs) in Incheon between July 2024 and April 2025. The results showed that ToBRFV was detected in all influent samples (240/240), with concentrations ranging from 7.42 to 9.91 log10 gene copies/L and low coefficients of variation (3.36%-6.39%). The observed concentrations were significantly higher than those reported from other regions in previous studies, confirming high abundance and stable detection of ToBRFV. This study represents the first quantitative assessment of ToBRFV in Korean wastewater using digital PCR. These findings suggest that ToBRFV has potential as a reliable human fecal contamination indicator and normalization marker for wastewater-based epidemiology (WBE) applications in Korean wastewater systems.