Molecular epidemiology of norovirus in South Korea

Surge of acute gastroenteritis outbreaks due to rising norovirus GII.4 transmission in Seoul childcare centers and kindergartens in 2022 compared to 2019-2021

Noroviruses are the most common cause of acute gastroenteritis (AGE) outbreaks in childcare centers and kindergartens. Their high transmissibility is partly due to their genetic diversity. AGE outbreaks that occurred in Seoul childcare centers and kindergartens from 2019 to 2022 were investigated, and 68 epidemiological reports prepared by public health centers in Seoul were used for data collection. In the three quarters of 2022, there were 40 outbreaks of AGE in Seoul childcare centers and kindergartens, which exceeded the 35 total outbreaks that occurred during the previous three years. The proportion of childcare centers and kindergartens with AGE outbreaks among all facilities in Seoul increased from 12.6% in 2019 to 58.8% in 2022. Noroviruses were the most common pathogens responsible for AGE outbreaks in these cases. From 2019 to 2021, norovirus GII.2 was the predominant genotype, and GII.4 was detected in about 25% of cases. However, in 2022, GII.4 became predominant and was detected in about 79% of cases. The attack rate and infection source of AGE outbreaks from 2019 to 2021 were not significantly different from those in 2022. In conclusion, the number of AGE outbreaks in Seoul childcare centers and kindergartens increased significantly, primarily because of increased norovirus GII.4 transmission in 2022.

A narrative review of norovirus epidemiology, biology, and challenges to vaccine development

Norovirus is a leading cause of acute gastroenteritis (AGE) globally. AGE resulting from norovirus causes significant morbidity and mortality in countries of all income levels, particularly among young children and older adults. Prevention of norovirus AGE represents a unique challenge as the virus is genetically diverse with multiple genogroups and genotypes cocirculating globally and causing disease in humans. Variants of the GII.4 genotype are typically the most common genotype, and other genotypes cause varying amounts of disease year-to-year, with GII.2, GII.3, and GII.6 most prevalent in recent years. Noroviruses are primarily transmitted via the fecal-oral route and only a very small number of virions are required for infection, which makes outbreaks of norovirus extremely difficult to control when they occur. Settings like long-term care facilities, daycares, and hospitals are at high risk of outbreaks and can have very high attack rates resulting in substantial costs and disease burden. Severe cases of norovirus AGE are most common in vulnerable patient populations, such as infants, the elderly, and immunocompromised individuals, with available treatments limited to rehydration therapies and supportive care. To date, there are no FDA-approved norovirus vaccines; however, several candidates are currently in development. Given the substantial human and economic burden associated with norovirus AGE, a vaccine to prevent morbidity and mortality and protect vulnerable populations could have a significant impact on global public health.

Prevalence of Eleven Infectious Viruses Causing Diarrhea in Korea

Rotavirus and norovirus are well-known causes of viral infectious diarrhea. There are few reports on diarrhea caused by other viruses in Korea, although cases of gastroenteritis attributable to other viruses are increasing worldwide. The aims of this study were to detect various causes of viral diarrhea and to investigate their prevalence. A total of 801 fecal specimens submitted to a clinical microbiology laboratory for the detection of diarrheal viruses were included. We sought to detect rotavirus A/B/C, adenovirus, astrovirus, norovirus GI/GII, sapovirus, Aichi virus, human parechovirus, enterovirus, human cosavirus, human bocavirus, and Saffold virus using multiplex reverse transcription polymerase chain reaction (RT-PCR). At least one diarrheal virus was detected in 223 (27.8%) fecal specimens. Among them, two viruses were detected in 11 specimens. Rotavirus A was most common (17.1%; N = 137), followed by norovirus GII (5.0%; N = 40), enterovirus (4.2%; N = 34), adenovirus (1.0%; N = 8), astrovirus (1.0%; N = 8), human parechovirus (0.6%; N = 5), and human bocavirus (0.2%; N = 2). Rotaviruses B and C, norovirus GI, sapovirus, Aichi virus, human cosavirus, and Saffold virus were not detected. We confirmed that various diarrheal viruses can be detected in fecal specimens. We must consider the possibility of viruses other than rotavirus and norovirus being present in cases of diarrhea.

Research on the contamination levels of norovirus in food facilities using groundwater in South Korea, 2015-2016

Norovirus (NoV) is a major pathogenic virus that is responsible for foodborne and waterborne gastroenteritis outbreaks. Groundwater is an important source of drinking water and is used in agriculture and food manufacturing processes. This study investigated norovirus contamination of groundwater treatment systems at 1360 sites in seven metropolitan areas and nine provinces in 2015-2016. Temperature, pH, residual chlorine, and turbidity content were assessed to analyze the water quality. In 2015, six sites were positive for the presence of NoV (0.88%) and in 2016, two sites were positive (0.29%); in total, NoV was detected in 8 of the 1360 sample sites (0.59%) investigated. Identified genotypes of NoV in groundwater included GI.5, 9 and GII.4, 6, 13, 17, and 21. GII.17 was the most prevalent genotype in treated groundwater used in the food industry. This dominance of GII.17 was corroborated by NoV infection outbreak cases and the results of a survey of coastal waters in South Korea in 2014-2015. Although a low detection rate was observed in this study, NoV is a pathogen that can spread extensively. Therefore, it is necessary to periodically monitor levels of norovirus which is responsible for food poisoning in groundwater. This is a first report to reveal epidemic genotype shift of norovirus in groundwater treatment system of food facilities in South Korea. Our results may contribute to the enhancement of public health and sanitary conditions by providing molecular epidemiological information on groundwater NoV.

Genetic and epidemiological analysis of norovirus from children with gastroenteritis in Botswana, 2013-2015

Background

Norovirus is a leading cause of viral gastroenteritis worldwide with a peak of disease seen in children. The epidemiological analysis regarding the virus strains in Africa is limited. The first report of norovirus in Botswana was in 2010 and currently, the prevalence and circulating genotypes of norovirus are unknown, as the country has no systems to report the norovirus cases. This study investigated the prevalence, patterns and molecular characteristics of norovirus infections among children ≤5 years of age admitted with acute gastroenteritis at four hospitals in Botswana.

Methods

A total of 484 faecal samples were collected from children who were admitted with acute gastroenteritis during the rotavirus vaccine impact survey between July 2013 and December 2015. Norovirus was detected using real-time RT-PCR. Positive samples were genotyped using conventional RT-PCR followed by partial sequencing of the capsid and RdRp genes. Norovirus strains were determined by nucleotide sequence analysis using the online Norovirus Genotyping Tool Version 1.0, and confirmed using maximum likelihood tree construction as implemented in MEGA 6.0.

Results

The prevalence of norovirus was 9.3% (95% CI 6.7–11.9). The genotype diversity was dominated by the GII.4 strain at 69.7%. This was followed by GII.2, GII.12 each at 9.1%, GI.9 at 6.6% and GII.6, GII.10 each at 3.0%. The most common combined RdRp/Capsid genotype was the GII.Pe/GII.4 Sydney 2012. Norovirus was detected during most part of the year; however, there was a preponderance of cases in the wet season (December to March).

Conclusion

The study showed a possible decline of norovirus infections in the last 10 years since the first report. An upward trend seen between 2013 and 2015 may be attributable to the success of rotavirus vaccine introductions in 2012. Knowledge of circulating genotypes, seasonal trends and overall prevalence is critical for prevention programming and possible future vaccine design implications.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3157-y) contains supplementary material, which is available to authorized users.

Enteric Viruses in Surface Waters from Argentina: Molecular and Viable-Virus Detection

Water resources contaminated with wastewater are an important source for the dissemination of enteric viruses with an impact on the health of the population. The aim of the study was to assess the viral contamination of freshwater from a dam in Argentina by using infectious enterovirus detection, viral RNA amplification, and a genetic characterization of five enteric viruses associated with diarrhea and hepatitis. Enterovirus infectivity (iEV) was evaluated by cell culture and direct immunofluorescence. The detection of the viral genome of rotavirus (RV), human astrovirus (HAstV), norovirus (NoV), hepatitis A virus (HAV), and hepatitis E virus (HEV) was performed by reverse transcriptase PCR (RT-PCR). A total of 48 water samples from 4 monitoring points on the body of the dam from January to December 2012 and 66 water samples from 3 tourist beaches on the edge of the dam from October 2013 to October 2015 were collected monthly. During the first period, the overall viral frequency detection was 52.1% for group A RV, 50% for HAstV, 60.4% for NoV, 22.9% for HAV, 2.1% for HEV, and 64.6% for iEV. The overall frequency detection for the second sampling was 18.2% for RV and HAstV, 31.8% for NoV, 7.57% for HEV, and 66.7% for iEV. There was no detection of HAV during this period. The genotypes and genogroups detected through the study correlated with the most common genomic variants associated with human gastrointestinal and hepatitis illnesses. The results obtained could alert the health systems and environmental sanitation to make decisions for viral control and prevention in our environment.IMPORTANCE The study shows the impact of anthropic contamination of one of the most important tourist water resources in Argentina. This course of recreational water would be a favorable scenario for infection, as well as a reservoir for the enteric viruses, creating a risk for the population exposed to these waters. The results obtained could alert the health systems and environmental sanitation to make decisions for the control and prevention of viral diseases in this environment.

Occurrence of novel GII.17 and GII.21 norovirus variants in the coastal environment of South Korea in 2015

Human norovirus (HNoV), a positive-sense RNA virus, is the main causative agent of acute viral gastroenteritis. Multiple pandemic variants of the genogroup II genotype 4 (GII.4) of NoV have attracted great attention from researchers worldwide. However, novel variants of GII.17 have been overtaking those pandemic variants in some areas of East Asia. To investigate the environmental occurrence of GII in South Korea, we collected water samples from coastal streams and a neighboring waste water treatment plant in North Jeolla province (in March, July, and December of 2015). Based on capsid gene region C analysis, four different genotypes (GII.4, GII.13, GII.17, and GII.21) were detected, with much higher prevalence of GII.17 than of GII.4. Additional sequence analyses of the ORF1-ORF2 junction and ORF2 from the water samples revealed that the GII.17 sequences in this study were closely related to the novel strains of GII.P17-GII.17, the main causative variants of the 2014-2015 HNoV outbreak in China and Japan. In addition, the GII.P21-GII.21 variants were identified in this study and they had new amino acid sequence variations in the blockade epitopes of the P2 domain. From these results, we present two important findings: 1) the novel GII.P17-GII.17 variants appeared to be predominant in the study area, and 2) new GII.21 variants have emerged in South Korea.