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Thitapa Longum. The Molecular Characterization of Human Norovirus and Sapovirus Detected in Pediatric Patients with Acute Gastroenteritis in Chiang Mai, Thailand. Master's degree(Microbiology). Chiang Mai University. Library. : Chiang Mai University, 2024.
The Molecular Characterization of Human Norovirus and Sapovirus Detected in Pediatric Patients with Acute Gastroenteritis in Chiang Mai, Thailand
Abstract:
Acute gastroenteritis is a significant cause of diarrhea and mortality among children under 5 years old worldwide. Norovirus and sapovirus are the major pathogens responsible for acute gastroenteritis. Both viruses exhibit high diversity and are widely distributed globally. The purpose of this study is to investigate the prevalence and genetic diversity of norovirus and sapovirus genotypes circulating in Chiang Mai, Thailand, from January 2021 to December 2023. A total of 1,031 stool samples were collected from pediatric patients younger than 5 years old who were hospitalized with acute gastroenteritis. Norovirus was detected by using real time RT-PCR, while sapovirus was screened by using RT-PCR. The positive samples for norovirus or sapovirus were further characterized their nucleotide sequences of RdRp and VP1 genes by Sanger sequencing method. These sequences were used for genetic characterization by comparing the nucleotide sequences with those of the previously reported available strains in the GenBank database and were analyzed by phylogenetic analysis. The results revealed that among 1,031 samples, norovirus was detected in 173 (16.8%), while sapovirus was detected in 18 (1.8%). The lowest infection rates were observed in 2021, which was the duration of COVID-19 pandemic in Thailand. However, the infection rates for both viruses increased in 2022-2023 when the control measures for COVID-19 pandemic situation were relaxed. During the three-year study period, norovirus was detected year-round and the peak of infections occurred from October to March. In contrast, sapovirus was detected sporadically. The norovirus genotypes, based on VP1 gene, were comprised of 14 genotypes, including GI.3, GI.4, GI.5, GI.6, GII.2, GII.3, GII.4, GII.6, GII.7, GII.8, GII.10, GII.17, GII.21, and GIX.1. Of these, GII.4 was identified as the most predominant genotype, with GII.4 Sydney 2012 being the primary variant detected. Additionally, GII.4 San Francisco variant was also identified, which had not been previously reported in Thailand. Based on RdRp gene, 10 P-types of norovirus were identified from nucleotide sequences of the RdRp gene, including GI.P4, GI.P6, GII.P7, GII.P8, GII.P12, GII.P15, GII.P16, GII.P17, GII.P21, and GII.P31. Of these, GII.P16 and GII.P31 were the most prevalent P-types. The dual typing of RdRp and VP1 genes revealed that 14 distinct patterns were identified, including GI.4[P4], GI.5[P4], GI.6[P6], GII.2[P16], GII.3[P12], GII.4[P16], GII.4[P31], GII.6[P7], GII.7[P7], GII.8[P8], GII.10[P16], GII.17[P17], GII.21[P21], and GIX.1[P15], with GII.4[P31] being the most predominant genotype. For sapovirus, based on RdRp gene, 7 genotypes, GI.1, GI.6, GII.5, GII.6, GII.8, GIV.1, and GV.2 were identified, while based on VP1 gene 5 genotypes, GI.1, GI.6, GII.5, GII.8, and GIV.1 were identified. Of these, GI.1 was the most prevalent sapovirus genotype identified in this study. It was interesting to point out that this study is the first report of sapovirus genotypes GI.6, GII.8, and GV.2 in Thailand. Furthermore, the recombination analysis demonstrated that the novel inter-genogroup recombination between GII.5 (RdRp) and GI.1 (VP1) was identified in this study. To the best of our knowledge, this kind of inter-genogroup recombinant strain had not been reported previously. Phylogenetic analysis revealed that norovirus and sapovirus strains detected in this study were closely related to several strains previously reported from various countries worldwide both in clinical samples from human and water samples. It can be concluded that the findings of this study reveal the prevalent and genetic diversity of norovirus and sapovirus in pediatric patients with acute gastroenteritis in Chiang Mai, Thailand from 2021 to 2023. These information are valuable for epidemiological studies and for developing strategies to prevent outbreaks of these viruses in the future.