Key result
Norovirus GII predominates in Black Sea mussels but shows no correlation with E. coli levels.
Why the study?
Bivalve mollusks bioaccumulate human enteric viruses and pose food safety risks, warranting assessment of Norovirus, Hepatitis A, and Hepatitis E prevalence along the Bulgarian Black Sea coast.
Observational (n=59)
Current bacterial indicators may be insufficient to ensure viral safety in bivalve mollusks, as viral RNA was detected in samples complying with bacterial standards.
Current bacterial indicators may miss norovirus in compliant mussels; leaves open need for viral-specific monitoring standards.
Bivalve mollusks efficiently bioaccumulate human enteric viruses, posing significant food safety risks. This study assessed the prevalence of Norovirus (NoV GI and NoV GII), Hepatitis A virus (HAV), and Hepatitis E virus (HEV) in 59 samples of live mussels (Mytilus galloprovincialis) collected from the Bulgarian Black Sea coast between July 2022 and July 2023. Viral detection was performed using one-step real-time reverse transcription-polymerase chain reaction (RT-qPCR) following ISO 15216-2 standards, with a mean extraction efficiency of 4.06%. Norovirus GII was the most prevalent pathogen, with detection peaks following intense rainfall events in July 2023. In contrast, all samples tested negative for HAV and HEV. The analysis showed no significant correlation between E. coli contamination levels and the presence of NoV (Mann–Whitney U test, p = 0.565). The viral RNA was detected in several samples that otherwise complied with regulatory bacterial standards for direct consumption (≤230 MPN/100 g). In conclusion, within the limitations of the evaluated sample size and the specific geographically unbalanced sampling design, NoV GII was the predominant genogroup detected. These results suggest that current bacterial indicators may be insufficient to ensure viral safety in these products. In this regard, national control authorities need to undertake timely policies and measures for better and adequate surveillance, control and prevention of viruses in the different parts of the food chain.
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Krumova-Valcheva et al. (2026) conducted an observational in Viral contamination in bivalve mollusks (n=59). Norovirus GII was the predominant pathogen detected in 59 mussel samples from the Bulgarian Black Sea coast, showing no significant correlation with E. coli contamination levels (p=0.565).
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