Emergence of norovirus GII.17[P16] during the COVID-19 outbreak in Thailand, 2021−2023

Leera Kittigul, Department of Microbiology, Faculty of Public Health, Mahidol University, Bangkok, Thailand

Leera Kittigul1, Thongthiw Pairoh1, Kitwadee Rupprom2, Yuwanda Thongpanich1, Sukhontha Siri3 1Department of Microbiology, Faculty of Public Health, Mahidol University, Bangkok, Thailand. 2Department of Clinical Pathology, Faculty of Medicine Vajira Hospital, Navamindradhiraj University, Bangkok, Thailand. 3Department of Epidemiology, Faculty of Public Health, Mahidol University, Bangkok, Thailand.

Molecular Epidemiology & Evolution

Noroviruses are an important cause of acute gastroenteritis in humans across all age groups. While GII.4 is the predominant strain, GII.17 has been frequently detected in patients with acute gastroenteritis. Here, we reported norovirus prevalence, genotypes and viral load in adult patients attending two hospitals in Thailand during the COVID-19 outbreak from December 2021 to March 2023. The prevalence of norovirus GII infection was at 11.2% (28/250 stool samples), whereas norovirus GI was not detected in any of the collected stool samples. Based on phylogenetic analysis for the open reading frame (ORF) 1/ORF2 junction region, GII.17 (82.1%) norovirus was a dominant genotype followed by GII.4 (10.7%), GII.3 (3.6%), and GII.2 (3.6%). Genetic analysis of RdRp and VP1 genes showed GII.4 Sydney[P31], GII.17[P17], and GII.17[P16] with GII.17[P16] being the most frequently identified genotype.
Norovirus GII-infected patients with GII.4 Sydney[P31] had a higher viral concentration (8.31 × 109 genome copies/g) than GII.17[P17] (8.93 × 105 − 4.46 × 108 genome copies/g) and GII.17[P16] (3.70 × 104 − 1.58 × 107 genome copies/g). This study provides epidemiological information of norovirus in adult patients with acute gastroenteritis contributing new insights for norovirus evolution, outbreak prevention and vaccine development.