Emerging norovirus GII.4 Sydney[P31] causing acute gastroenteritis outbreak in children in Japan, during COVID-19, 2021

The viral trends and genotype diversity of norovirus in the wastewater of Shenzhen, China

Norovirus (NoV) is the primary cause of acute gastroenteritis (AGE) on a global scale. Numerous studies have demonstrated the immense potential of wastewater surveillance in monitoring the prevalence and spread of NoV within communities. This study employed a one-step reverse transcription-quantitative PCR to quantify NoV GI/GII in wastewater samples (n = 2574), which were collected once or twice a week from 38 wastewater treatment plants from March 2023 to February 2024 in Shenzhen. The concentrations of NoV GI and GII ranged from 5.0 × 104 to 1.7 × 106 copies/L and 4.1 × 105 to 4.5 × 106 copies/L, respectively. The concentrations of NoV GII were higher than those of NoV GI. Spearman's correlation analysis revealed a moderate correlation between the concentration of NoV in wastewater and the detection rates of NoV infections in sentinel hospitals. Baseline values were established for NoV concentrations in Shenzhen's wastewater, providing a crucial reference point for implementing early warning systems and nonpharmaceutical interventions to mitigate the impact of potential outbreaks. A total of 24 NoV genotypes were identified in 100 wastewater samples by sequencing. Nine genotypes of NoV GI were detected, with the major genotypes being GI.4 (38.6 %) and GI.3 (21.8 %); Fifteen genotypes of NoV GII were identified, with GII.4 (53.6 %) and GII.17 (26.0 %) being dominant. The trends in the relative abundance of NoV GI/GII were significantly different, and the trends in the relative abundance of NoV GII.4 over time were similar across all districts, suggesting a potential risk of cross-regional spread. Our findings underscore the effectiveness of wastewater surveillance in reflecting population-level NoV infections, capturing the diverse array of NoV genotypes, and utilizing NoV RNA in wastewater as a specific indicator to supplement clinical surveillance data, ultimately enhancing our ability to predict the timing and intensity of NoV epidemics.

Rotavirus outbreaks in China, 1982-2021: a systematic review

Background

Rotavirus is globally recognized as an important cause of acute gastroenteritis in young children. Whereas previous studies focused more on sporadic diarrhea, the epidemiological characteristics of rotavirus outbreaks have not been systematically understood.

Methods

This systematic review was carried out according to the Preferred Reporting Items for Systematic Review and Meta-Analysis standards, WANFANG, China National Knowledge Infrastructure (CNKI), PubMed, and Web of Science databases were searched from database inception to February 20, 2022. We used SPSS 21.0 statistical software for data analysis, RStudio1.4.1717, and ArcGIS trial version for plotting bar graphs and maps.

Results

Among 1,596 articles, 78 were included, with 92 rotavirus outbreaks and 96,128 cases. Most outbreaks (67.39%, 62/92) occurred in winter and spring. The number of rotavirus outbreaks reported in the eastern region was more than that in the western region. Outbreaks were most commonly reported in villages (33/92, 35.87%), followed by hospitals (19, 20.65%). The outbreak duration was longer in factories and workers' living places, and villages, while it was shorter in hospitals. Waterborne transmission was the main transmission mode, with the longest duration and the largest number of cases. Rotavirus groups were identified in 66 outbreaks, with 40 outbreaks (60.61%) caused by Group B rotaviruses and 26 outbreaks (39.39%) caused by Group A rotaviruses. Significant differences were found in duration, number of cases, settings, population distribution, and transmission modes between Groups A and B rotavirus outbreaks.

Conclusion

Rotavirus is an important cause of acute gastroenteritis outbreaks in China. It should also be considered in the investigation of acute gastroenteritis outbreaks, especially norovirus-negative outbreaks.

An unusual diarrheal outbreak in the community in Eastern Thailand caused by Norovirus GII.3[P25]

BACKGROUND

Sentinel laboratory surveillance for diarrheal disease determined norovirus to be the most common cause of non-bacterial gastroenteritis in people during the COVID-19 pandemic in Thailand. An increase in patients presenting with diarrhea and vomiting in hospitals across Chanthaburi province between December 2021 and January 2022 led to the need for the identification of viral pathogens that may be responsible for the outbreak.

METHODS

Fecal samples (rectal swabs or stool) from 93 patients, of which 65 patients were collected during the December 2021 to January 2022 outbreak, were collected and screened for viral infection by real-time RT-PCR. Positive samples for norovirus GII were then genotyped by targeted amplification and sequencing of partial polymerase and capsid genes. Full genome sequencing was performed from the predominant strain, GII.3[P25].

RESULTS

Norovirus was the most common virus detected in human fecal samples in this study. 39 of 65 outbreak samples (60%) and 3 of 28 (10%) non-outbreak samples were positive for norovirus genogroup II. One was positive for rotavirus, and one indicated co-infection with rotavirus and norovirus genogroups I and II. Nucleotide sequences of VP1 and RdRp gene were successfully obtained from 28 of 39 positive norovirus GII and used for dual-typing; 25/28 (89.3%) were GII.3, and 24/28 (85.7) were GII.P25, respectively. Norovirus GII.3[P25] was the predominant strain responsible for this outbreak. The full genome sequence of norovirus GII.3[P25] from our study is the first reported in Thailand and has 98.62% and 98.57% similarity to norovirus found in China in 2021 and the USA in 2022, respectively. We further demonstrate the presence of multiple co-circulating norovirus genotypes, including GII.21[P21], GII.17[P17], GII.3[P12] and GII.4[P31] in our study.

CONCLUSIONS

An unusual diarrhea outbreak was found in December 2021 in eastern Thailand. Norovirus strain GII.3[P25] was the cause of the outbreak and was first detected in Thailand. The positive rate during GII.3[P25] outbreak was six times higher than sporadic cases (GII.4), and, atypically, adults were the primary infected population rather than children.

Tracking the effects of the COVID-19 pandemic on viral gastroenteritis through wastewater-based retrospective analyses

The COVID-19 pandemic possibly disrupted the circulation and seasonality of gastroenteritis viruses (e.g., Norovirus (NoV), Sapovirus (SaV), group A rotavirus (ARoV), and Aichivirus (AiV)). Despite the growing application of wastewater-based epidemiology (WBE), there remains a lack of sufficient investigations into the actual impact of the COVID-19 pandemic on the prevalence of gastroenteritis viruses. In this study, we measured NoV GI and GII, SaV, ARoV, and AiV RNA concentrations in 296 influent wastewater samples collected from three wastewater treatment plants (WWTPs) in Sapporo, Japan between October 28, 2018 and January 12, 2023 using the highly sensitive EPISENS™ method. The detection ratios of SaV and ARoV after May 2020 (SaV: 49.8 % (134/269), ARoV: 57.4 % (151/263)) were significantly lower than those before April 2020 (SaV: 93.9 % (31/33), ARoV: 97.0 % (32/33); SaV: p < 3.5×10-7, ARoV: p < 1.5×10-6). Furthermore, despite comparable detection ratios before (88.5 %, 23/26) and during (66.7 %, 80/120) the COVID-19 pandemic (p = 0.032), the concentrations of NoV GII revealed a significant decrease after the onset of the pandemic (p < 1.5×10-7, Cliff's delta = 0.72). NoV GI RNA were sporadically detected (24.7 %, 8/33) before April 2020 and after May 2020 (6.5 %, 17/263), whereas AiV was consistently (100 %, 33/33) detected from wastewater throughout the study period (95.8 %, 252/263). The WBE results demonstrated the significant influence of COVID-19 countermeasures on the circulation of gastroenteritis viruses, with variations observed in the magnitude of their impact across different types of viruses. These epidemiological findings highlight that the hygiene practices implemented to prevent COVID-19 infections may also be effective for controlling the prevalence of gastroenteritis viruses, providing invaluable insights for public health units and the development of effective disease management guidelines.

Genetic diversity and declining norovirus prevalence in infants and children during Japan's COVID-19 pandemic: a three-year molecular surveillance

Noroviruses (NoVs) are a global concern, causing widespread outbreaks and sporadic acute gastroenteritis (AGE) cases across all age groups. Recent research has shed light on the emergence of novel recombinant strains of NoV in various countries. To delve deeper into this phenomenon, we extensively analyzed 1,175 stool samples collected from Japanese infants and children with AGE from six different prefectures in Japan over three years, from July 2018 to June 2021. Our investigation aimed to determine the prevalence and genetic characteristics of NoV associated with sporadic AGE while exploring the possibility of detecting NoV recombination events. Among the analyzed samples, we identified 355 cases positive for NoV, 11 cases attributed to GI genotypes, and 344 associated with GII genotypes. Notably, we discovered four distinct GI genotypes (GI.2, GI.3, GI.4, and GI.6) and seven diverse GII genotypes (GII.2, GII.3, GII.4, GII.6, GII.7, GII.14, and GII.17). The predominant genotypes were GII.4 (56.4%; 194 out of 344), followed by GII.2 and GII.3. Through dual genotyping based on sequencing of the ORF1/ORF2 junction region, we identified a total of 14 different RdRp/capsid genotypes. Of particular interest were the prevalent recombinant genotypes GII.4[P31] and GII.2[P16]. Notably, our study revealed a decrease in the number of children infected with NoV during and after the COVID-19 pandemic. These findings underscore the importance of continuous NoV surveillance efforts.

Prevalence of Human Norovirus GII.4 Sydney 2012 [P31] between 2019 and 2021 among Young Children from Rural Communities in South Africa

Acute gastroenteritis (AGE) accounts for considerable morbidity and mortality in the paediatric population worldwide, especially in low-income countries. Human norovirus (HNoV), particularly GII.4 strains, are important agents of AGE. This study aimed to detect and characterise HNoV in children with and without AGE. Between 2019 and 2021, 300 stool samples (200 AGE and 100 without AGE) were collected from children below 5 years of age referred to the healthcare facilities of the rural communities of Vhembe District, South Africa. After detection using real-time RT-PCR, HNoV positive samples were subjected to RT-PCR and Sanger sequencing. Partial nucleotide sequences (capsid/RdRp) were aligned using the Muscle tool, and phylogenetic analysis was performed using MEGA 11. The nucleotides' percent identity among HNoV strains was compared using ClustalW software. A significant difference in HNoV prevalence between AGE children (37%; 74/200) and non-AGE (14%; 14/100) was confirmed (p < 0.0001). Genogroup II (GII) HNoV was predominant in AGE children (80%; 59/74), whereas most non-AGE children were infected by the GI norovirus genogroup (64%; 9/14). GII.4 Sydney 2012 [P31] strains were dominant (59%; 19/32) during the study period. A phylogenetic analysis revealed a close relationship between the HNoV strains identified in this study and those circulating worldwide; however, ClustalW showed less than 50% nucleotide similarity between strains from this study and those from previously reported norovirus studies in the same region. Our findings indicate significant changes over time in the circulation of HNoV strains, as well as the association between high HNoV prevalence and AGE symptoms within the study area. The monitoring of HuNoV epidemiology, along with stringent preventive measures to mitigate the viral spread and the burden of AGE, are warranted.

Outbreak of human astroviruses 1 and Melbourne 2 in acute gastroenteritis pediatric patients in Japan during the COVID-19 pandemic, 2021

BACKGROUND

Human astrovirus (HAstV) infection is one of the leading causes of acute gastroenteritis in young children. The present study reports the outbreak of HAstV in children with acute gastroenteritis in Kyoto, Japan, during the COVID-19 pandemic, 2021.

METHODS

A total of 61 stool samples were collected from children with acute gastroenteritis who visited a pediatric outpatient clinic in Maizuru city, Kyoto, Japan from July to October, 2021. HAstV was screened by RT-PCR, and the genotypes were identified by nucleotide sequence analysis.

RESULTS

Of 61 cases of acute gastroenteritis, 20 were mono-infected with HAstV alone. In addition, mixed infection of HAstV and NoV, and HAstV and RVA were also detected in 15 and 1 cases, respectively. Of 36 HAstV strains detected in this outbreak, 29 and 7 were HAstV1 and MLB2 genotypes, respectively. All HAstV1 strains were closely related to the HAstV1 reported from Thailand and Japan in 2021 and all of them belonged to subgenotype HAstV1a. Among MLB2, they were most closely related to the MLB2 strains reported from China in 2016 and 2018.

CONCLUSIONS

After the kindergartens and schools were re-opened at the middle of 2021 in Japan, an outbreak of HAstV was reported. Control measures against the COVID-19 pandemics might affect the spread of diarrheal virus infection. Here we report the outbreak of HAstV1 and MLB2 in Kyoto, Japan, during COVID-19 pandemic in 2021.

[Molecular epidemiology and evolution of human noroviruses]

Noroviruses are the most common viral cause of acute gastroenteritis after the introduction of rotavirus vaccines. Norovirus infection can cause severe symptoms in vulnerable populations including young children and the elderly. Thus, it is still a leading cause of death from diarrhea in children in developing countries. Recent advancement of genomics platforms facilitated understanding of the epidemiology of norovirus, while the whole picture of norovirus diversity is still undetermined. Currently, there are no approved vaccines for norovirus, but state-of-the-art norovirus cultivation systems could elucidate the antigenic diversity of this fast-evolving virus. In this review, we will summarize the historical and latest findings of norovirus epidemiology, diversity, and evolution.