Abstract

This study evaluated norovirus detection in bivalves collected from a high-energy open-water (HEO) aquaculture farm located approximately 15 km offshore from Gusipo on the west coast of Korea and from comparative coastal sites. Diploid and triploid Pacific oysters (Crassostrea gigas) and pen shells (Atrina pectinata) cultured at the HEO farm, together with wild oysters from Gochang and farmed oysters from Geoje and Goheung, were analyzed for norovirus GI and GII by one-step RT-qPCR from July 2024 to November 2025. To accommodate differences in study objectives and sample characteristics, the survey was conducted in three sequential phases consisting of preliminary pooled screening, individual-based confirmation, and long-term pooled monitoring. No norovirus was detected in any shellfish samples collected from the HEO farm throughout the 17-month survey period, including the winter season when norovirus contamination is generally more prevalent. In contrast, wild diploid oysters from Gochang tested positive for both GI and GII in January 2025, and farmed diploid oysters from Geoje tested positive for GII in February and March 2025. Farmed triploid oysters from Goheung remained negative throughout the monitored period. These findings indicate that shellfish produced in the offshore HEO environment had no detectable norovirus during the study period and suggest that such environments, being physically separated from land-based contamination sources, may represent a lower-risk setting for shellfish production with respect to norovirus contamination.