Genotypic and Epidemiological Trends of Acute Gastroenteritis Associated with Noroviruses in China from 2006 to 2016

Prevalence and genotype distribution of norovirus in Ningxia Hui Autonomous Region, China, from 2011 to 2022

The norovirus (NoV) genome is diverse. Therefore, this study explored the epidemiological characteristics and genetic features of NoV in Ningxia Hui Autonomous Region, China, from 2011 to 2022 to clarify the genetic diversity in this region. Stool samples were screened for NoV and then sequenced and genotyped. In total, 1,788 of 13,083 specimens were NoV -positive (13.67%); 204 (1.56%) and 1,584 (12.11%) cases were GI and GII, respectively. Additionally, 559 were NoV infection with other viruses (4.27%), primarily with rotavirus (277/559, 49.55%). The NoV incidence rate was the highest among children aged 0-2 years (18.09%, 1054/5,828) and lowest among adults aged 45-64 years (110/1,495, 7.36%); it was also higher in the winter and spring than in the other seasons. GI.3[P3] was the dominant GI genotype. The dominant GII genotype changed roughly every two years. In the GII group, GII.4 was the most common genotype (46.79%), followed by GII.3 (21.34%), GII.2 (12.34%), and GII.17 (9.77%). There were three variants of GII.4 Den Haag, GII.4 New Orleans and GII.4 Sydney identified in the detected GII.4 strains, with GII.4 Sydney dominating. The GII.4 (87.36%), GII.3 (86.35%), and GII.2 (72.92%) strains were primarily detected in children, whereas it was the GII.17 (52.63%) strain in adults. Overall, the NoV genotypes in the Ningxia Hui Autonomous Region were diverse. Primarily, GII groups were dominant, but this changed over time.

Improving knowledge, attitude and practice on norovirus infection diarrhea among staff of kindergartens and schools: a before-after study

BACKGROUND

Norovirus gastroenteritis outbreaks were common in schools and kindergartens and were more related to faculty knowledge, attitude, and practice level. Gastroenteritis outbreaks caused by norovirus in educational institutions were the prominent cause of Public Health Emergency Events in China. This study aimed to explore the transformation in the contribution of KAP items related to outbreak prevention before and after intervention and the impact of demography factors on the intervention.

METHODS

This study sampled 1095 kindergarten and 1028 school staff in Shenzhen, China. We created a questionnaire consisting of 35 items in 4 parts, and each item was rated on a scale of 1-5 according to the accuracy. Univariate analysis of non-parametric tests and binary logistic regression were used to estimate the score difference on demographic characteristics, each item and KAP. The odds ratios (OR) with 95% confidence and intervals (CI) for the association between statistical indicators were mainly used to explain the effects before and after intervention.

RESULTS

Overall, 98.72% and 74.9% of the kindergarten and school participants were female, and all respondents had the highest scores difference of practice. Following intervention, univariate analysis indicated that primary school and female respondents achieved higher knowledge scores. Staff age beyond 35 (OR = 0.56, CI:0.34-0.92; OR = 0.67, CI:0.50-0.90) and with more than ten years of service (OR = 0.58, CI:0.36-0.91; OR = 0.38, CI:0.17-0.84) demonstrated a significantly lower post-intervention score for attitude and practice in both kindergartens and schools. The staff members exhibited a general lack of familiarity with the transmission of aerosols and the seasonal patterns of NoVs diarrhea pandemics. Item analysis revealed that kindergarten staff aged 26 and above demonstrated superior performance in terms of the efficacy of medical alcohol for inactivation (OR = 1.93, CI:1.13-3.31) and management strategies for unexplained vomiting among students (OR = 1.97, CI:1.21-3.18). Private school personnel displayed more significant improvement in their practices following educational interventions. School administrators' negative attitudes were primarily evident in their perspectives on morning inspections (OR = 0.11, CI:0.05-0.84).

CONCLUSIONS

The potential negative impact of faculty age on NoVs-related knowledge can be mitigated by the positive attitudes fostered through seniority. Furthermore, it is imperative to urgently address the lack of knowledge among administrators, and the identification and treatment of vomiting symptoms should be emphasized as crucial aspects of school prevention strategies. Therefore, education authorities should implement comprehensive public health interventions in the future.

Detection rates of norovirus gastroenteritis and factors associated with the infection before and during COVID-19 pandemic: a secondary analysis of surveillance data in Guangxi Zhuang Autonomous Region, Southern China

Background: Changes in oral and hand hygiene behaviors have been reported during the COVID-19 pandemic in 2020 which may be associated with the incidence of the norovirus infection, a common cause of gastroenteritis. Objective: To estimate the trends of detection rates of norovirus gastroenteritis and associated factors before COVID-19 in 2015-2019 and during the COVID-19 in 2020 in Guangxi, China. Methods: A secondary analysis of Guangxi surveillance data of gastroenteritis patients was conducted. The detection rate in 2020 was predicted using an autoregressive integrated moving average modeland associated factors were analyzed using multiple logistic regression adjusted for interaction effects. Results: Of 7,903 gastroenteritis patients, the overall detection rate of norovirus gastroenteritis was 12.8%, (14.3% before and 6.1% during COVID-19). Detection rates gradually decreased from 2015 to 2020, of which the slope of predicted line was slightly flatter than the actual line. The odds ratios of detection were double to triple increase during COVID-19 in the younger age group and having food intake outside their homes. Tourist city, season, and types of food were independent associated factors. Conclusion: The detection rates were higher during the COVID-19 year among the population aged 45 years or less and those who consumed food outside their home.

Biological Specimen Banking as a Time Capsule to Explore the Temporal Dynamics of Norovirus Epidemiology

Norovirus is recognised as a major cause of epidemic and sporadic acute gastroenteritis (AGE) in all age groups. Information on the genetic diversity of the noroviruses circulating in the 1980s and 1990s, before the development and adoption of dedicated molecular assays, is limited compared with the last decades. Between 1986 and 2020, uninterrupted viral surveillance was conducted in symptomatic children hospitalized with AGE in Palermo, Italy, providing a unique time capsule for exploring the epidemiological and evolutionary dynamics of enteric viruses. A total of 8433 stool samples were tested using real-time RT-PCR. All samples were stored at -20 or -80 °C until processing. In this 35-year long time span, noroviruses of genogroup II (GII) were detected in 15.6% of AGE requiring hospitalization, whilst GI noroviruses were detected in 1.4% of AGE. Overall, the predominant norovirus capsid (Cap) genotype was GII.4 (60.8%), followed by GII.3 (13.3%) and GII.2 (12.4%). Temporal replacement of the GII.4 Cap variants associated with different polymerase (Pol) types were observed over the study period. The chronology of emergence and circulation of the different GII.4 variants were consistent with data available in the literature. Also, for GII.3 and GII.2 NoVs, the circulation of different lineages/strains, differing in either the Cap or Pol genes or in both, was observed. This long-term study revealed the ability of noroviruses to continuously and rapidly modify their genomic makeup and highlights the importance of surveillance activities in vaccine design.

Prevalence and Etiological Characteristics of Norovirus Infection in China: A Systematic Review and Meta-Analysis

Norovirus is a common cause of sporadic cases and outbreaks of gastroenteritis worldwide, although its prevalence and the dominant genotypes responsible for gastroenteritis outbreaks remain obscure. A systematic review was conducted on norovirus infection in China between January 2009 and March 2021. A meta-analysis and beta-binomial regression model were used to explore the epidemiological and clinical characteristics of norovirus infection and the potential factors contributing to the attack rate of the norovirus outbreaks, respectively. A total of 1132 articles with 155,865 confirmed cases were included, with a pooled positive test rate of 11.54% among 991,786 patients with acute diarrhea and a pooled attack rate of 6.73% in 500 norovirus outbreaks. GII.4 was the predominant genotype in both the etiological surveillance and outbreaks, followed by GII.3 in the etiological surveillance, and GII.17 in the outbreaks, with the proportion of recombinant genotypes increasing in recent years. A higher attack rate in the norovirus outbreaks was associated with age group (older adults), settings (nurseries, primary schools, etc.) and region (North China). The nation-wide pooled positive rate in the etiological surveillance of norovirus is lower than elsewhere in the global population, while the dominant genotypes are similar in both the etiological surveillance and the outbreak investigations. This study contributes to the understanding of norovirus infection with different genotypes in China. The prevention and control of norovirus outbreaks during the cold season should be intensified, with special attention paid to and enhanced surveillance performed in nurseries, schools and nursing homes from November to March.

Spatio-temporal distribution and influencing factors of norovirus outbreaks in Beijing, China from 2016 to 2020

BACKGROUND

Noroviruses are a leading cause of acute gastroenteritis (AGE) worldwide. The geographical characteristics of norovirus outbreaks in Beijing and their influencing factors remain unknown. This study aimed to explore the spatial distributions, geographical characteristics, and influencing factors of norovirus outbreaks in Beijing, China.

METHODS

Epidemiological data and specimens were collected through the AGE outbreak surveillance system in all 16 districts of Beijing. Data on spatial distribution, geographical characteristics, and influencing factors of norovirus outbreaks were analyzed using descriptive statistics methods. We measured spatial, geographical clustering of high- or low-value deviance from random distribution using Z-scores and P-values as statistical significance measures with Global Moran's I statistics and Getis-Ord Gi in ArcGIS. Linear regression and correlation methods were used to explore influencing factors.

RESULTS

Between September 2016 and August 2020, 1,193 norovirus outbreaks were laboratory-confirmed. The number of outbreaks varied seasonally, typically peaking in spring (March to May) or winter (October to December). Outbreaks primarily occurred around central districts at the town level, and spatial autocorrelation was evident in both the entire study period and in individual years. Hotspots of norovirus outbreaks in Beijing were primarily found in contiguous areas between three central districts (Chaoyang, Haidian, Fengtai) and four suburban districts (Changping, Daxing, Fangshan, Tongzhou). The average population numbers, mean number of all schools, and mean number of kindergartens and primary schools for towns in central districts and hotspot areas were higher than those in suburban districts and non-hotspot areas respectively. Additionally, population numbers and densities of kindergartens and primary schools were influencing factors at the town level.

CONCLUSIONS

Hotspots of norovirus outbreaks in Beijing were in contiguous areas between central and suburban districts with high populations, and high kindergarten and primary school densities were the likely driving forces. Outbreak surveillance needs to focus on contiguous areas between central and suburban districts with increased monitoring, medical resources, and health education.

Evaluation of the transmissibility of norovirus and the effectiveness of prevention and control measures for schools in Jiangsu Province

OBJECTIVE

This study aims to estimate the transmissibility of norovirus outbreaks in schools by different transmission routes, and to evaluate the effects of isolation, school-closure and disinfection measures under different intervention intensities, finally, scientific prevention and control suggestions are proposed.

METHOD

23 outbreaks of norovirus infectious diarrhea occurring in Jiangsu Province's school from 2012-2018 were selected and fitted to the model. The data includes various types of school places and pathogen genotype. A 'SEIAQRW' model with two transmission routes was established. The transmissibility of each outbreak was assessed using effective reproduction number, the efficacy of different intervention measures and intensities were evaluated by calculating the total attack rate and peak incidence.

RESULTS

The mean effective reproduction number of noroviruses was estimated to be 8.92 for the human-to-human route of transmission and 2.19 for the water or food-to-human route of transmission. When all symptomatic cases were isolated, the median peak incidence for both transmission routes both being less than 1.8%. There was a smaller reduction in total attack rate compared to peak incidence, the median total attack rate for the two transmission routes decreased by 17.59% and 42.09%, respectively. When the effect of school-closure or disinfection is more than 90%, the total attack rate and peak incidence in the human-to-human route are reduced by more than 90% compared to no intervention, and the peak incidence in the water or food-to-human routes can be reduced to less than 1.4%, but the reduction in the total attack rate is only 50% or so.

CONCLUSION

Norovirus outbreaks have a high rate of transmission in schools. In the case of norovirus outbreaks, isolation should be complemented by other interventions, and the implementation of high-intensity school closures or disinfection of the external environment can be effective in reducing the spread of the virus.

Norovirus outbreaks in China, 2000-2018: A systematic review

To understand epidemiological characteristics of norovirus outbreaks in China from 2000 to 2018 the literature on norovirus outbreaks was identified by searching WANFANG, CNKI, PubMed, and Web of Science databases before 31 December 2018. Statistical analyses were performed using Statistical Product Service Solutions software. RStudio1.4.1717 and ArcGIS trial version were used for plotting bar graphs and maps. A total of 419 norovirus outbreaks were reported in the 394 included articles, which occurred between June 2000 and October 2018, showing an overall increasing trend. The majority of outbreaks occurred in schools (52.28%, 218/417) and kindergartens (55/417, 13.19%). Person-to-person transmission (41.64%, 137/329) was most common, followed by food-borne transmission (75/329, 22.80%) and water-borne transmission (72/329, 21.88%). GII was the most predominant norovirus genogroup, with GII.4, GII.17 and GII.2 being the dominant genotypes in 2007-2013, 2014-2015, 2016-2017, respectively. Increased outbreaks were associated with the prevalence of new variants. Most norovirus outbreaks were reported in the southeast of the country. The number of norovirus outbreaks was positively associated with the per capita gross domestic product and the year-end resident population. Norovirus outbreaks have become an important public health problem in China. It is necessary to establish surveillance in hospitals and nursing homes. Genotyping of noroviruses is important for monitoring the circulating strains and improving the vaccine design, so it should be carried out in more regions.

Epochal coevolution of minor capsid protein in norovirus GII.4 variants with major capsid protein based on their interactions over the last five decades

Norovirus is a leading cause of viral gastroenteritis outbreaks worldwide, with GII.4 responsible for the majority of infections. Minor capsid protein VP2 has been found to have functions such as stabilizing virus particles, and VP2 is one of the highly variable proteins of norovirus, similar to major capsid protein VP1. However, whether the variation of VP2 is functionally driven still remains unclear. In this study, VP2 showed a higher evolutionary rate (2.642×10^-3 substitutions/site/year) than VP1 (1.587×10^-3 substitutions/site/year), and a hypervariable region in VP2 in a serial of norovirus GII.4 over the past 50 years had been observed. Notably, the high variation of VP2 was not haphazard. The evolutionary process of VP2 is similar to that of VP1 with comparable topologies when the phylogenetic trees were constructed. Moreover, VP2 was found to interact with VP1 among epidemic variants of GII.4 using the yeast two-hybrid experiments. The results of interactions were grouped into time-adjacent (e.g. Ancestral-VP1 plus US95-VP2) and non-adjacent (e.g. Ancestral-VP1 plus Sydney-VP2) according to the epochal chronologically based prevalence of GII.4 norovirus. Interestingly, the interaction of the former group was significantly stronger than that of the latter group (P=0.0001). Furthermore, the interaction regions on VP2 (residues 131-160 and 171-180) were mapped to the hypervariable region. And these interaction regions did show an important role in the evolutionary process of VP2, which was consistent with that of VP1. In summary, the minor capsid protein VP2 of GII.4 noroviruses had shown the epochal coevolution with VP1 based on their interactions over the past 50 years. The findings of this study provided valuable information for further understanding and completing the evolutionary mechanism of norovirus.

Updating a New Semi-nested PCR Primer Pair for the Specific Detection of GII Norovirus in Oysters

Oysters are major transmission vectors of noroviruses (NoVs) in the environment. Outbreaks of NoVs are often associated with the consumption of NoV-contaminated oysters. Laboratory confirmation of suspected oyster samples is a critical step in the surveillance and control of NoVs. Because of non-specific amplification, false-positive results are frequently obtained by semi-nested RT-PCR with the presently widely used primer set (G2SKF/G2SKR). Here, a novel universal PCR primer set N (NG2OF/NG2OR) specific for genogroup II (GII) NoVs was designed based on all GII NoV sequences available in public databases. Specific products were obtained with the primer set N when the NoV-positive oysters, spiked with each of five representative genotypes of GII NoVs (GII.17, GII.13, GII.4, GII.3, and GII.12), were subjected to analyzing. No products were detected with the primer set N for the NoV-negative oysters, while the primer set C gave various non-specific bands. Twenty-three out of 156 fresh oyster samples were NoV-positive with both the primer set N and the classic primer set, while eight were NoV-positive solely with the primer set N. Compared with the classic primer set, the newly designed primer set N had a higher detection rate and improved specificity for GII NoVs in oyster samples. These results show that the novel PCR primer pair is specific and applicable for the detection of GII NoVs in oysters.

Investigation and analysis on an outbreak of norovirus infection in a health school in Guangdong Province, China

Our objective was to describe the epidemiological features of an outbreak of norovirus infection in a health school in Guangdong province, China, to identify the cause of such a large scale outbreak of norovirus among older students, to simulate the transmission dynamics, and to evaluate the effect of intervention measures of GII.17 [P17] genotype norovirus infection. We identified all cases during the outbreak. Descriptive epidemiological, analytical epidemiological and hygiene survey methods were used to described the outbreak epidemic course and identify the cause of the outbreak of norovirus infection. We also used dynamical model to simulate the transmission dynamics of norovirus infection and evaluate the effect of intervention measures. Norovirus genotyping was assigned to the newly obtained strains, with a maximum likelihood phylogenetic analysis conducted. There were 360 cases of 42 classes in five grades with a 12.99% attack rate. Proportionally, more students were in contact with sick students and vomit in the suspected case group than the control group (χ² = 5.535, P = 0.019 and χ² = 5.549, P = 0.019, respectively). The basic reproduction number was 8.32 before and 0.49 after the intervention. Dynamical modeling showed that if the isolation rate was higher or case isolation began earlier, the total attack rate would decrease. Molecular characterization identified the GII.17 [P17] genotype in all stains obtained from the health school, which were clustered with high support in the phylogenetic tree. This was an outbreak of norovirus infection caused by contact transmission. The main reasons for the spread of the epidemic were the later control time, irregular treatment of vomit and no case isolation. The transmission dynamics of contact transmission was high, more efficient control measures should be employed.

Norovirus GII.2[P16] strain in Shenzhen, China: a retrospective study

Background

Norovirus (NoV) is the main cause of non-bacterial acute gastroenteritis (AGE) outbreaks worldwide. From September 2015 through August 2018, 203 NoV outbreaks involving 2500 cases were reported to the Shenzhen Center for Disease Control and Prevention.

Methods

Faecal specimens for 203 outbreaks were collected and epidemiological data were obtained through the AGE outbreak surveillance system in Shenzhen. Genotypes were determined by sequencing analysis. To gain a better understanding of the evolutionary characteristics of NoV in Shenzhen, molecular evolution and mutations were evaluated based on time-scale evolutionary phylogeny and amino acid mutations.

Results

A total of nine districts reported NoV outbreaks and the reported NoV outbreaks peaked from November to March. Among the 203 NoV outbreaks, 150 were sequenced successfully. Most of these outbreaks were associated with the NoV GII.2[P16] strain (45.3%, 92/203) and occurred in school settings (91.6%, 186/203). The evolutionary rates of the RdRp region and the VP1 sequence were 2.1 × 10^–3 (95% HPD interval, 1.7 × 10^–3–2.5 × 10^–3) substitutions/site/year and 2.7 × 10^–3 (95% HPD interval, 2.4 × 10^–3–3.1 × 10^–3) substitutions/site/year, respectively. The common ancestors of the GII.2[P16] strain from Shenzhen and GII.4 Sydney 2012[P16] diverged from 2011 to 2012. The common ancestors of the GII.2[P16] strain from Shenzhen and previous GII.2[P16] (2010–2012) diverged from 2003 to 2004. The results of amino acid mutations showed 6 amino acid substitutions (*77E, R750K, P845Q, H1310Y, K1546Q, T1549A) were found only in GII.4 Sydney 2012[P16] and the GII.2[P16] recombinant strain.

Conclusions

This study illustrates the molecular epidemiological patterns in Shenzhen, China, from September 2015 to August 2018 and provides evidence that the epidemic trend of GII.2[P16] recombinant strain had weakened and the non-structural proteins of the recombinant strain might have played a more significant role than VP1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06746-9.

Prevalence of GII.4 Sydney Norovirus Strains and Associated Factors of Acute Gastroenteritis in Children: 2019/2020 Season in Guangzhou, China

Norovirus, the leading cause of non-bacterial acute gastroenteritis (AGE) worldwide, is constantly mutating. Continuous monitoring of the evolution of epidemic genotypes and emergence of novel genotypes is, therefore, necessary. This study determined the prevalence and clinical characteristics of norovirus strains in AGE in Guangzhou, China in 2019/2020 season. This study included children aged 2-60 months diagnosed with AGE in Guangzhou Women and Children Hospital, from August 2019 to January 2020. Norovirus was detected by real-time polymerase chain reaction and clinical data were obtained. Genotyping and phylogenetic analyses were performed with partial gene sequence fragments located within the open reading frames 1 and 2. During the study period, 168 children (61.3% males) were confirmed as norovirus infectious AGE. The main symptoms were diarrhoea and vomiting and 38 patients (22.6%) had seizures. Norovirus was mainly prevalent in October and November, and GII.4 Sydney[P31] was the major genotype circulating in Guangzhou. The phylogenetic tree showed that the Guangzhou strains had high homology with the strains circulating in 2017-2019 worldwide. GII.4 Sydney was the main prevalent norovirus genotype in Guangzhou from August 2019 to January 2020, which had more severe diarrhoea than those of other genotypes. These findings provide a valuable reference for the prevention, control, and treatment of norovirus in the future.

Evolution of the interactions between GII.4 noroviruses and histo-blood group antigens: Insights from experimental and computational studies

Norovirus (NoV) is the major pathogen causing the outbreaks of the viral gastroenteritis across the world. Among the various genotypes of NoV, GII.4 is the most predominant over the past decades. GII.4 NoVs interact with the histo-blood group antigens (HBGAs) to invade the host cell, and it is believed that the receptor HBGAs may play important roles in selecting the predominate variants by the nature during the evolution of GII.4 NoVs. However, the evolution-induced changes in the HBGA-binding affinity for the GII.4 NoV variants and the mechanism behind the evolution of the NoV-HBGA interactions remain elusive. In the present work, the virus-like particles (VLPs) of the representative GII.4 NoV stains epidemic in the past decades were expressed by using the Hansenula polymorpha yeast expression platform constructed by our laboratory, and then the enzyme linked immunosorbent assay (ELISA)-based HBGA-binding assays as well as the molecular dynamics (MD) simulations combined with the molecular mechanics/generalized born surface area (MMGBSA) calculations were performed to investigate the interactions between various GII.4 strains and different types of HBGAs. The HBGA-binding assays show that for all the studied types of HBGAs, the evolution of GII.4 NoVs results in the increased NoV-HBGA binding affinities, where the early epidemic strains have the lower binding activity and the newly epidemic strains exhibit relative stronger binding intensity. Based on the MD simulation and MMGBSA calculation results, a physical mechanism that accounts for the increased HBGA-binding affinity was proposed. The evolution-involved residue mutations cause the conformational rearrangements of loop-2 (residues 390–396), which result in the narrowing of the receptor-binding pocket and thus tighten the binding of the receptor HBGAs. Our experimental and computational studies are helpful for better understanding the mechanism behind the evolution-induced increasing of HBGA-binding affinity, which may provide useful information for the drug and vaccine designs against GII.4 NoVs.

Human norovirus (NoV) has been recognized as the leading cause of the epidemic acute gastroenteritis worldwide and more than 50% acute gastroenteritis outbreaks are associated with NoVs. NoVs are highly infectious and may result in serious dehydration, malnutrition and even death, which severely threatens human health and brings heavy economic burden. NoVs are highly genetically diverse, in which the GII.4 genotype is the most predominant. The reported outbreaks of NoV infections have risen sharply from 2002, and it is suggested that the increasing NoV infections are attributed to the emergence of new strains with more infectiousness. GII.4 NoV evolves rapidly and on average every 2–3 years a new strain appears. It has been revealed that the histo-blood group antigens (HBGAs) serve as the recognition receptor for the GII.4 NoVs infecting the host cell, and the NoV-HBGA interactions may play an important role in selecting the predominate variants during the evolution of GII.4 NoVs. However, the molecular mechanism behind the evolution of the NoV-HBGA binding affinities is still not clear. In this work, the representative GII.4 NoV strains prevalent in the past decades were expressed, and the changes in the interactions between these strains and the receptor HBGAs were investigated by using the experimental measurements combined with computational simulations. Based on the experimental and computational results, a molecular mechanism that accounts for the increasing of the NoV-HBGA binding affinities during the evolution of GII.4 NoVs was proposed. Our studies are helpful for the understanding of the evolution mechanism of GII.4 NoVs and provide valuable information for the drug and vaccine designs against GII.4 NoVs.

Norovirus Outbreak Surveillance, China, 2016-2018

CaliciNet China, a network of provincial, county, and city laboratories coordinated by the Chinese Centers for Disease Control and Prevention, was launched in October 2016 to monitor the epidemiology and genotype distribution of norovirus outbreaks in China. During October 2016–September 2018, a total of 556 norovirus outbreaks were reported, and positive fecal samples from 470 (84.5%) outbreaks were genotyped. Most of these outbreaks were associated with person-to-person transmission (95.1%), occurred in childcare centers or schools (78.2%), and were reported during November–March of each year (63.5%). During the 2-year study period, 81.2% of all norovirus outbreaks were typed as GII.2[P16]. In China, most norovirus outbreaks are reported by childcare centers or schools; GII.2[P16] is the predominant genotype. Ongoing surveillance by CaliciNet China will provide information about the evolving norovirus genotype distribution and outbreak characteristics important for the development of effective interventions, including vaccines.

An acute gastroenteritis outbreak associated with breakfast contaminated with norovirus by asymptotic food handler at a kindergarten in Shenzhen, China

Background

An outbreak of acute gastroenteritis occurred in a kindergarten located Shenzhen City on March 4, 2018. We were invited to investigate to the risk factors associated with this outbreak.

Methods

We conducted retrospective cohort-studies on three different groups of subjects in order to figure out the difference of incidence of acute gastroenteritis among subjects of different activities on March 2: group one consisted of people who attended the Lantern festival activities; group two consisted of children and employees who ate breakfast and bread provided by the kindergarten; and groups three consisted of children and employees who did not eat breakfast or bread provided by the kindergarten. Fecal, anal swabs, dishware swabs and hand swabs specimens were collected in the study. Bacteria known to cause acute gastroenteritis were cultured. Viruses associated with acute gastroenteritis were tested using real-time PCR. Capsid gene fragment of 557 bp of norovirus was amplified and sequenced. The phylogenetic tree was constructed with MEGA 7.0 using neighbor-joining method based on capsid gene fragment of norovirus.

Results

A total of 143 suspected cases were identified in this outbreak. Diarrhea happened more often in adults than in children while emesis and bellyache were more frequently found in children than in adults. Higher AGE incidence was observed in group 2, children and employees who had breakfast in the kindergarten on March 2, as well as in group 3, and among employees who eating bread involved in breakfast provided on March 2. Five anal swab specimens were positive for norovirus. All noroviruses belongs to group II.3 and have an identity more than 99%.

Conclusion

A chef, as an asymptomatic carrier with norovirus, was the infectious resource in this outbreak. He contaminated breakfast food provided on March 2. Although morning check is implemented in kindergartens of China, employees are often excluded in morning check. Our finding highlights the importance of morning check covering employees and periodical training for cooks.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05762-z.

An increasing prevalence of non-GII.4 norovirus genotypes in acute gastroenteritis outbreaks in Huzhou, China, 2014-2018

Since 2014, novel non-GII.4 norovirus (NoV) genotypes continue to be reported as the main cause of outbreaks worldwide. In this study, we analyzed the epidemiological and genetic features of NoV outbreaks from July 2014 to June 2018 in Huzhou, China. A total of 450 stool samples collected from 51 AGE outbreaks were tested for NoVs by real-time RT PCR. Partial polymerase and capsid sequences of NoV-positive samples were amplified and sequenced for phylogenetic analysis. NoVs were found to be responsible of 84.3% of AGE outbreaks in Huzhou over the past 5 years. Most NoV outbreaks were reported in the cool months (November-March) and occurred in primary schools and kindergartens. Changes in the diversity of genotypes and the distribution of predominant types were observed in recent years. At least eight genotypes were identified, and 91.9% of the genotyped outbreaks were caused by non-GII.4 strains. The top three circulating genotypes during the study period were GII.2[P16], GII.3[P12], and GII.17[P17]. The predominant NoV genotypes in outbreaks have changed from GII.4 variants to GII.17[P17] in 2014-2015, GII.3[P12] in 2015-2016, and then GII.2[P16] in 2016-2018. Non-GII.4 NoVs play an increasingly important role in outbreaks in Huzhou. Continuous surveillance is needed to monitor the emergence of novel NoV strains and help control NoV outbreaks in the next epidemic season.

Epidemiologic characteristics of outbreaks of three norovirus genotypes (GII.2, GII.17 and GII.4 Sydney) in Guangzhou, China, from 2012 to 2018

To compare the epidemiologic features (e.g. settings and transmission mode) and patient clinical characteristics associated with outbreaks of different norovirus (Nov) strains, we retrospectively analysed data of Nov outbreaks occurring in Guangzhou, China from 2012 to 2018. The results suggested that outbreaks of Nov GII.2, GII.17 and GII.4 Sydney exhibited different outbreak settings, transmission modes and symptoms. GII.2 outbreaks mainly occurred in kindergartens, elementary and high schools and were transmitted mainly through person-to-person contact. By contrast, GII.4 Sydney outbreaks frequently occurred in colleges and were primarily associated with foodborne transmission. Cases from GII.2 and GII.17 outbreaks reported vomiting more frequently than those from outbreaks associated with GII.4 Sydney.

Genotypic prevalence of norovirus GII in gastroenteritis outpatients in Shanghai from 2016 to 2018

BACKGROUND

With the help of an existing citywide comprehensive surveillance on gastroenteritis outpatients, although norovirus genogroup II (NoV GII) was tested routinely, its genotypes were never investigated systematically on a municipal level. This study aimed to understand the prevalence, major genotypes and evolutional trends of NoV GII in Shanghai during the period of 2016-2018, and to provide molecular bases for early warning for any potential NoV outbreaks.

METHODS

27 sentinel hospitals from all 16 districts were recruited by stratified probability proportional to size (PPS) method in Shanghai comprehensive diarrhea surveillance programme. Stool samples were collected and screened for NoV GII by real-time reverse transcription polymerase chain reaction (qRT-PCR). For samples that were positive in qRT-PCR, conventional RT-PCR was performed to amplify the ORF1-ORF2 junction of NoV GII gene. Generated sequences were typed by RIVM online genotyping tool, and then strains of interest were analyzed phylogenetically using MEGA 6.0.

RESULTS

A total of 7883 stool samples were collected from diarrhea outpatients, among which 6474 were from adults and 1409 were from children. 13.66% (1077 cases) were screened positive in qRT-PCR for NoV GII, from which 71.96% (775 cases) were sequenced successfully. The top three genotypes were GII.Pe/GII.4 (37%), GII.P17/GII.17 (26%) and GII.P16/GII.2 (17%). While GII.Pe/GII.4 detection rate decreased significantly over the 3 years (from 48.4 to 20.9%); GII.P16/GII.2 appeared for the first time in October 2016 and rose rapidly to 27.0% in 2017, but fell back to 23.4% in 2018. Meanwhile there was a significant increase for both GII.P12/GII.3 and GII.P7/GII.6 recombinant genotypes detected in adult population in 2018. Phylogenic analysis revealed the existence of multiple gene clusters within both of these recombinant genotypes.

CONCLUSION

Unlike the alternating circulation of GII.4 and non-GII.4 NoV observed in 2016 or 2017, the genotype profile of NoV GII in 2018 was characterized by the co-prevalence of multiple recombinant genotypes. A recent increase in detection rate in less reported recombinant genotypes such as GII.P12/GII.3 and GII.P7/GII.6 among adult population calls for a continuing close monitoring on NoV GII genotypes in case of potential local outbreaks.

Prevalence of noroviruses in children hospitalized for acute gastroenteritis in Hohhot, China, 2012-2017

BACKGROUND

Noroviruses (NVs) are an important cause of acute gastroenteritis (AGE) worldwide. There are limited data on the prevalence and molecular characterization of NVs in children in Hohhot, China.

METHODS

Between January 2012 and December 2017, 1863 stool samples were collected at Maternal and Child Health Hospital in Hohhot. All samples were screened for NVs by real-time reverse transcription polymerase chain reaction (real-time RT-PCR).

RESULTS

NVs were detected in 24.15% of these inpatient cases, ranging from 12.78 to 32.92% in different years. NV was detected throughout the year, with a peak in winter. Based on sequence analysis of the partial VP1 gene, the 306 identified NV strains were divided into six genotypes: GII.3 (71.24%), GII.4 (23.53%), and GII.2, GII.5, GII.6, and GII.13 (total 5.23%). Based on further sequence analysis of the RNA-dependent RNA polymerase (RdRp), GII.P12/GII.3, GII.Pe/GII.4, and GII.P4/GII.4 were identified as predominant genotypes, accounting for 92.6% of genotyped strains. The median age of the children with NV infection was 8.0 (range 0-59) months. However, children infected with GII.3 were younger (median 7.0 months) than GII.4-positive patients (median 10.0 months).

CONCLUSION

NV contributed greatly to AGE among hospitalized children in Hohhot in China. Continuous surveillance is important for understanding the local prevalence and characterization of NV.

Recalibration of the Grunow-Finke Assessment Tool to Improve Performance in Detecting Unnatural Epidemics

Successful identification of unnatural epidemics relies on a sensitive risk assessment tool designed for the differentiation between unnatural and natural epidemics. The Grunow-Finke tool (GFT), which has been the most widely used, however, has low sensitivity in such differentiation. We aimed to recalibrate the GFT and improve the performance in detection of unnatural epidemics. The comparator was the original GFT and its application in 11 historical outbreaks, including eight confirmed unnatural outbreaks and three natural outbreaks. Three steps were involved: (i) removing criteria, (ii) changing weighting factors, and (iii) adding and refining criteria. We created a series of alternative models to examine the changes on the parameter likelihood of unnatural outbreaks until we found a model that correctly identified all the unnatural outbreaks and natural ones. Finally, the recalibrated GFT was tested and validated with data from an unnatural and natural outbreak, respectively. A total of 238 models were tested. Through the removal of criteria, increasing or decreasing weighting factors of other criteria, adding a new criterion titled "special insights," and setting a new threshold for likelihood, we increased the sensitivity of the GFT from 38% to 100%, and retained the specificity at 100% in detecting unnatural epidemics. Using test data from an unnatural and a natural outbreak, the recalibrated GFT correctly classified their etiology. The recalibrated GFT could be integrated into routine outbreak investigation by public health institutions and agencies responsible for biosecurity.

An Outbreak of Gastroenteritis Associated with GII.17 Norovirus-Contaminated Secondary Water Supply System in Wuhan, China, 2017

A gastroenteritis outbreak occurred in a university in May, 2017, Wuhan, China. The epidemiological survey and pathogen analysis were conducted to identify the pathogen and control this outbreak. Feces or anal swabs from individuals, water, and swabs taken from tap surfaces of the secondary water supply system (SWSS) and foods were collected for the detection of viruses and pathogenic enteric bacteria by real-time RT-PCR and culture, respectively. Nucleotide sequences were determined by RT-PCR and direct sequencing. Genotyping, phylogenetic, and recombination analyses were conducted by a web-based genotyping tool, MEGA, and RDP4 programs, respectively. Of 144 individuals enrolled, 75 met the case definitions. The epidemic curve showed one peak of incidence suggesting the most probable spread of a single common source. In total, 33 specimens were collected before disinfection of the SWSS. Of these, norovirus was detected and identified as GII.P17-GII.17 with 100% nucleotide sequence identity among the strains detected in ten students (10/14), a maintenance worker (1/2) dealing with the SWSS, four water samples (4/8), and two swabs taken from tap surfaces (2/3). Pathogens including Vibrio cholerae, Salmonella, Shigella, Vibrio parahaemolyticus, Bacillus cereus, enteropathogenic Escherichia coli, rotavirus, astrovirus, and sapovirus were negative. The GII.17 strains in this outbreak clustered closely in the same branch of the phylogenetic tree, and slightly apart from the strains of other cities in China, neighboring countries and regions, European and American countries. This gastroenteritis outbreak was deduced to be attributed to GII.P17-GII.17 norovirus contamination of the SWSS.

Diagnostic determination of Norovirus infection as one of the major causes of infectious diarrhea in HIV patients using a multiplex polymerase chain reaction assay

Although infectious diarrhea is one of the most common complications in human immunodeficiency virus (HIV)-infected patients, robust diagnostic methods for determining potential pathogens are still limited in the clinic. Norovirus, a type of calicivirus, has been shown to be the most common cause of gastroenteritis. Here, we used multiplex polymerase chain reaction as a diagnostic tool to verify Norovirus as the diarrhea-related pathogen in HIV-infected patients with unknown etiological information. Stool specimens obtained from 81 HIV-infected patients with diarrhea were analyzed by BioFire FilmArray Gastrointestinal (GI) panel. Among 26 HIV-infected patients with unknown etiological information, we detected Norovirus in 14 stool specimens of these patients with 100% sensitivity and specificity as confirmed by reverse transcription polymerase chain reaction (RT-PCR), and one specimen showed both Norovirus and enterotoxigenic Escherichia coli infection. Among the remaining 55 patients with verified Clostridium difficile infection, nine patients also detected positive for Norovirus infection. In conclusion, using FilmArray GI panel and RT-PCR, we determined that Norovirus infection as one of the main pathogens responsible for diarrhea in HIV patients.

Surveillance of norovirus contamination in commercial fresh/frozen berries from Heilongjiang Province, China, using a TaqMan real-time RT-PCR assay

Norovirus (NoV), a major food-borne virus, causes non-bacterial acute gastroenteritis in humans. Berries are generally harvested from low-growing bushes by hand and are minimally processed before being sold to consumers. Therefore, the consumption of berries has been linked to numerous food-borne gastroenteritis outbreaks caused by NoV in many countries. We performed a survey of NoV contamination in commercial fresh/frozen berry fruits collected from 2016 to 2017 in the Heilongjiang Province, the main berry-producing area in China, using a TaqMan-based real-time reverse transcription-PCR assay. Among 900 frozen and 900 fresh domestic retail berry samples, the prevalence of NoV was 9% (81/900) and 12.11% (109/900), including 35.80% (29/81) and 29.36% (32/109) of genotype GI alone, 54.32% (44/81) and 60.55% (66/109) of GII alone, and 9.88% (8/81) and 10.09% (11/109) of both GI and GII, respectively. No NoV was detected among the 677 frozen berry samples for export. Thus, the occurrence of NoV contamination was significantly higher in domestic berries than in exported berries and higher in fresh berries than in frozen berries. This study highlights the need for further risk surveillance for NoV contamination in berries produced in the Heilongjiang Province and recommends region-extended monitoring of retail berries for NoV.

The prevalence of non-GII.4 norovirus genotypes in acute gastroenteritis outbreaks in Jinan, China

Noroviruses (NoVs) are the leading cause of acute viral gastroenteritis outbreaks. From June 2015 to March 2017, fifteen outbreaks of acute gastroenteritis (AGE) were reported to the Jinan Center for Disease Control and Prevention in China. To identify the circulating NoV genotypes associated with outbreaks in Jinan, China, 414 specimens from the 15 outbreaks were collected and analyzed for the causative viruses, and phylogenetic analysis was performed on the NoV-positive strains. The NoV detection rate was 57.5% (238/414), and a total of 14 outbreaks were caused by NoVs (eight by infection with genogroup II (GII), five by mixed infection with GI and GII, and one by mixed infection with GII and rotavirus (RoV)-A). A total of 75 NoV sequences were obtained from 13 NoV-positive outbreaks and classified into seven genotypes (38 GII.17, 13 GII.2, 4 GII.3, 4 GII.1, 10 GI.6, 5 GI.5 and 1 GI.3), while GII.4 was not identified. The most prevalent genotype changed yearly during the 2015–2017 period. Phylogenetic analysis demonstrated that these NoV genotypes had high homology with the strains circulating worldwide, especially strains from Asian countries and cities. Our study illustrated that multiple non-GII.4 NoV genotypes were prevalent in outbreaks of AGE in Jinan, China. Year-round surveillance of multiple NoV genotypes could help health authorities reduce the impact of NoV outbreaks on public health.

Genomic characterization of GII.3 noroviruses isolated from children in Zhengzhou city, China, 2015/16

In this study, we isolated, amplified and sequenced GII.3 norovirus (NoV) strains from children admitted to a department of pediatric gastroenterology presenting with acute gastroenteritis from September 2015 to March 2016. A total of 35 stool samples were collected and eight were GII.3 NoV positive, based on sequencing. The complete genome sequences were determined for two strains while partial genome sequences, encompassing approximately 3.2 kb of the 3´end, were generated for the six other strains. Genotyping analysis of all strains indicated that they belonged to GII P12/GII.3. Phylogenetic analysis indicated that these isolated strains could be divided into two clusters. Strains in cluster IV were the most frequently isolated and exhibited less intra-cluster variation in nucleotide sequences. Our study demonstrated that the GII.P12/GII.3 recombinant strain was the dominant GII.3 NoVs in Zhengzhou city.