Viral bivalve contamination is a recognized food safety hazard. Therefore, this study investigated the detection rates, seasonality, quantification, and genetic diversity of enteric viruses in bivalve samples (mussels and oysters). We collected 97 shellfish samples between March 2018 and February 2020. The screening of samples by qPCR or RT-qPCR revealed the detection of norovirus (42.3%), rotavirus A (RVA; 16.5%), human adenovirus (HAdV; 24.7%), and human bocavirus (HBoV; 13.4%). There was no detection of hepatitis A virus. In total, 58.8% of shellfish samples tested positive for one or more viruses, with 42.1% of positive samples contaminated with two or more viruses. Norovirus showed the highest median viral load (3.3 × 10⁶ GC/g), followed by HAdV (median of 3.5 × 10⁴ GC/g), RVA (median of 1.5 × 10³ GC/g), and HBoV (median of 1.3 × 10³ GC/g). Phylogenetic analysis revealed that norovirus strains belonged to genotype GII.12[P16], RVA to genotype I2, HAdV to types -C2, -C5, and -F40, and HBoV to genotypes -1 and -2. Our results demonstrate the viral contamination of bivalves, emphasizing the need for virological monitoring programs to ensure the quality and safety of shellfish for human consumption and as a valuable surveillance tool to monitor emerging viruses and novel variants.

This study investigated the prevalence and genetic diversity of gastroenteric viruses in mussels and oysters in Rio de Janeiro, Brazil. One hundred and thirty-four marketed bivalve samples were obtained between January and December 2022. The viral analysis was performed according to ISO/TS 15216, and the screening revealed the detection of norovirus GII/GI (40.3%), sapovirus (SaV; 12.7%), human mastadenovirus (7.5%), and rotavirus A (RVA; 5.9%). In total, 44.8% (60) of shellfish samples tested positive for one or more viruses, 46.7% (28/60) of the positive samples tested positive for a single viral agent, 26.7% (16) tested positive for two viral agents, 8.3% (5) for three viral agents, and 13.3% (8) for four viral agents. Additionally, three mussel samples were contaminated with the five investigated viruses (5%, 3/60). Norovirus GII showed the highest mean viral load (3.4 × 10⁵ GC/g), followed by SaV (1.4 × 10⁴ GC/g), RVA (1.1 × 10⁴ GC/g), human mastadenovirus (3.9 × 10³ GC/g), and norovirus GI (6.7 × 10² GC/g). Molecular characterization revealed that the recovered norovirus strains belonged to genotypes GII.2, GII.6, GII.9, GII.17, and GII.27; SaV belonged to genotypes GI.1 and GIV.1; RVA to genotypes G6, G8, P[8]-III, and human mastadenovirus to types F40 and F41. The GII.27 norovirus characterized in this study is the only strain of this genotype reported in Brazil. This study highlights the dissemination and diversity of gastroenteric viruses present in commercialized bivalves in a touristic area, indicating the potential risk to human health and the contribution of bivalves in the propagation of emerging pathogens.

Human adenovirus (HAdV) F40/41 is an important pathogen in pediatric acute gastroenteritis cases. However, the diversity of study designs and diagnostic methods often leads to misinterpretations of their impact. Our study explored the genetic diversity of HAdV-F40/41 in Brazil using a specific qPCR assay for HAdV species F, combined with a phylogenetic analysis of the partial hexon and fiber genes. Our results demonstrated that HAdV-F41 strains predominated and exhibited higher diversity than HAdV-F40 strains. Based on the hexon gene, Brazilian HAdV-F41 strains were grouped into two genome type clusters (GTC), further divided into subclusters, with most strains clusteringto GTC2. The partial shaft region of the fiber gene exhibited higher conservation among HAdV-F41. The specific qPCR assay for HAdV species F identified HAdV-F in an additional 31.5% (34/108) of previously uncharacterized HAdV-positive samples detected using a non-specific HAdV qPCR assay. Both assays strongly correlated in detecting HAdV-F, and the specific qPCR assay for enteric types can enhance HAdV surveillance, especially when sequencing is not possible. Our study provides novel insights regarding the genetic diversity of HAdV-F species in Brazil.