Detection and Genetic Correlation Analysis of Diarrhea Cases and Norovirus in Oysters in Yantai, China

BACKGROUND: This study aimed to assess the correlation between Norovirus (NoV), diarrhea, and raw oysters from the eastern coastal areas of Yantai, Shandong, China. METHODS: Marine oysters were selected from the three aquatic markets in Laishan district, Yantai City, in March 2019. Meanwhile, 100 fecal samples were collected from patients with diarrhea from the same areas during the same period. Nucleic acids were extracted from these samples and detected by employing reverse transcription polymerase chain reaction (RT-PCR) for NoV GI/GII. The VP1 gene of the coat protein of NoV was amplified by semi-nested RT-PCR and sequenced. Sequence comparison of VP1 was performed with BioEdit software, and the evolutionary tree was constructed with Mega7.0 software. RESULTS: Of the 151 oysters, 42 (27.8%) were positive for NoV. Among them, 32 (21.2%) were GII-positive, 10 (6.6%) were GI-positive, and one GI VP1 sequence was obtained in the oyster samples. Of 100 fecal samples from patients with diarrhea, 38 were GII-positive and 17 were GI-positive. Totally, 19 GII VP 1 sequences and eight GI VP 1 sequences were obtained. Two G1 VP 1 sequences in two fecal samples showed 98.7% nucleotide sequence identity and 99.1% amino acid sequence identity G1 VP 1 acquired in the oyster sample. CONCLUSIONS: The results suggest that oysters may be responsible for the spread of NoV in Yantai, Shandong province, China.