Hyesook Jeong

Genetic analysis of norovirus GII.4 variants circulating in Korea in 2008

Noroviruses are the enteric pathogens most commonly responsible for infectious gastroenteritis and outbreaks of foodborne illness. The GII.4 norovirus, in particular, is responsible for the majority of epidemics. Here, we present data on the distribution of norovirus genotypes in Chungnam, Korea, in 2008, measure genetic variation among GII.4 strains, and compare Korean GII.4 variants with reference strains based on the 237-bp junction of ORF1 and ORF2. We detected 139 different strains, which formed two distinct genetic clusters with significant sequence diversity. One Korean cluster (2008-Korea_a) showed high similarity to the Sakai cluster that appeared in Japan and Europe in 2006. The other cluster (2008-Korea_b) was unique and unrelated to previously reported clusters. Genotype GII.4 was confirmed as the predominant cause of norovirus epidemics in Korea. Foodborne norovirus infections, on the other hand, were generally caused by emerging GII.4 genetic variants similar to those responsible for global epidemics.

Molecular epidemiology and genetic diversity of human astrovirus in South Korea from 2002 to 2007

The present study was conducted to survey the prevalence and genotypic distribution of human astrovirus (HAstV) circulating in South Korea. Of 160,027 patients with acute gastroenteritis, 2,057 (1.3%) were positive for HAstV antigen. We determined the genotypes of 187 HAstV strains collected from laboratories across the country. Genetic analysis revealed genotype 1 to be the most prevalent, accounting for 72.19% of the strains, followed by genotypes 8 (9.63%), 6 (6.95%), 4 (6.42%), 2 (3.21%) and 3 (1.60%). Our findings indicate that HAstV is less common but, even so, a potentially important viral agent of gastroenteritis in South Korea, with significant genetic diversity among circulating HAstV strains.

Occurrence of Norovirus Infections in Asymptomatic Food Handlers in South Korea

ABSTRACT Prevalence of asymptomatic norovirus infection was investigated in food handlers in South Korea. Among 6,441 subjects, 66 (1.02%) had norovirus infections confirmed by reverse transcription (RT)-PCR (real time and nested). GII-12 and GII-4 were the prevalent genotypes. Our data suggest that infection of asymptomatic food handlers is an important transmission source in norovirus outbreaks.

Murine norovirus-1 3Dpol exhibits RNA-dependent RNA polymerase activity and nucleotidylylates on Tyr of the VPg.

We investigated the roles and biochemical properties of recombinant murine norovirus-1 (MNV-1) 3D(pol) in RNA synthesis and virus genome-linked protein (VPg) nucleotidylylation. We therefore expressed VPg and 3D(pol) of MNV-1 in Escherichia coli. MNV-1 3D(pol) exhibited RNA-dependent RNA polymerase (RdRp) activity in vitro with poly(A) RNA as a template and MnCl(2) as a cofactor. MNV-1 3D(pol) demonstrated optimum RNA-synthesis activity at pH 7.4 and 37 degrees C in the absence of a primer. Further, VPg was guanylylated by MNV-1 3D(pol) in the presence of MnCl(2) in a template-independent manner. The guanylylation reaction conducted with VPg substitution mutants (Y26F, Y40F, Y45F and Y117F) and a deletion mutant (Delta117-124) indicated that Tyr(117) was the probable target site of guanylylation. Homopolymeric RNAs did not enhance VPg guanylylation, whereas in vitro-transcribed (-) subgenomic (SG) and (+)SG RNA enhanced VPg guanylylation by 9.2 and 3.2 times, respectively. Within (-)SG RNA, the (-)ORF3 region played a critical role in enhancing VPg guanylylation, suggesting that the MNV-1 ORF3 region of negative-strand RNA contains a cis-acting element that stimulates 3D(pol)-mediated VPg guanylylation.

Genotypes of the circulating rotavirus strains in the seven prevaccine seasons from September 2000 to August 2007 in South Korea

A Korean nationwide surveillance on circulating rotavirus strains was conducted from September 2000 to August 2007 aiming to obtain prevaccine data for predicting vaccine effectiveness. The predominant strains among the 2779 strains analyzed varied annually and only approximately 50% had either a G or a P antigen present in both RotaTeq (Merck & Co. Inc., Whitehouse Station, NJ, USA) and Rotarix (GlaxoSmithKline, Brentford, UK).

First norovirus outbreaks associated with consumption of green seaweed ( Enteromorpha spp.) in South Korea

In February 2012, an outbreak of gastroenteritis was reported in school A; a successive outbreak was reported at school B. A retrospective cohort study conducted in school A showed that seasoned green seaweed with radishes (relative risk 7·9, 95% confidence interval 1·1-56·2) was significantly associated with illness. Similarly, a case-control study of students at school B showed that cases were 5·1 (95% confidence interval 1·1-24·8) times more likely to have eaten seasoned green seaweed with pears. Multiple norovirus genotypes were detected in samples from students in schools A and B. Norovirus GII.6 isolated from schools A and B were phylogenetically indistinguishable. Green seaweed was supplied by company X, and norovirus GII.4 was isolated from samples of green seaweed. Green seaweed was assumed to be linked to these outbreaks. To our knowledge, this is the first reported norovirus outbreak associated with green seaweed.

Genetic Analysis of Hepatitis A Virus Strains That Induced Epidemics in Korea during 2007–2009

ABSTRACT Hepatitis A virus is one of the most prominent causes of fecally transmitted acute hepatitis worldwide. In order to characterize the viral agents causing an outbreak in Korea (comprising North and South Korea) from June 2007 to May 2009, we collected specimens and performed genotyping of the VP1/P2A and VP3/VP1 regions of hepatitis A virus. We then used a multiple-alignment algorithm to compare the nucleotide sequences of the 2 regions with those of reference strains. Hepatitis A virus antibodies were detected in 64 patients from 5 reported outbreaks (North Korea, June 2007 [n = 11]; Jeonnam, April 2008 [n = 15]; Daegu, May 2008 [n = 13]; Seoul, May 2009 [n = 22]; and Incheon, May 2009 [n = 3]). We found 100% homology between strains isolated from the Kaesong Industrial Region and Jeonnam. While those strains were classified as genotype IA strains, strains from Seoul and Incheon were identified as genotype IIIA strains and showed 98.9 to 100% homology. Genotype IIIA was also dominant in Daegu, where strains were 95.7 to 100% homologous. All hepatitis A virus strains isolated from the Kaesong Industrial Region, Jeonnam, Seoul, and Incheon belonged to a single cluster. However, strains from Daegu could be classified into 2 clusters, suggesting that the outbreak had multiple sources. This study indicates that hepatitis A virus strains of 2 different genotypes are currently cocirculating in Korea. Moreover, it documents an increasing prevalence of genotype IIIA strains in the country.

A Survey on the Status of Hepatitis E Virus Infection Among Slaughterhouse Workers in South Korea

Objectives: The seroprevalence of hepatitis E virus (HEV) among high-risk groups overseas is high, but studies in these groups are rare in South Korea. We conducted the present study from April to November 2012 to obtain data on the seroprevalence and associated risk factors for HEV among slaughterhouse workers in South Korea. Methods: Slaughterhouse workers from 80 workplaces nationwide were surveyed in South Korea in 2012. The subjects comprised 1848 cases: 1434 slaughter workers and 414 residual products handlers. By visiting 80 slaughterhouses, which were mixed with 75 of which also performed residual products handling, we conducted a questionnaire survey for risk factors and obtained blood samples in order to determine the seropositivity and seroprevalence of HEV. Anti-HEV IgG and IgM were measured using HEV IgG and IgM enzyme-linked immunospecific assay kits and HEV antigen was measured by reverse transcription polymerase chain reaction (RT-PCR). Results: The seropositivity of anti-HEV IgG was 33.5% (slaughter workers 32.8% and residual products handlers 36.2%), and among the seropositive individuals the seroprevalence of anti-HEV IgM was 0.5% (slaughter workers 0.5%, residual products handlers 0.7%). The response rate of HEV-antigen as measured by RT-PCR was 0.2%. Risk factors significantly related to anti-HEV IgG seropositivity were age, sex , and working duration (slaughter workers only). Conclusions: There were significant risk factors (sex, age, and working duration) for HEV identified in our study. All three positive cases for HEV-antigen by RT-PCR were related to pig slaughter but without statistical significance. To prevent HEV, an educational program and working guidelines may be needed for high risk groups.

Rotavirus diarrhea in hospitalized children under 5 years of age in Vientiane, Lao PDR, 2009–2015

BACKGROUND Diarrhea is a leading cause of death in children <5 years worldwide, causing an estimated 215,000 deaths in 2013. This evaluation tracks the epidemiologic patterns and most common rotavirus genotypes among hospitalized children in this age group with acute gastroenteritis in Lao PDR. METHODS Children <5 years in a central tertiary hospital in the capital city were prospectively enrolled into the surveillance platform during January 2009-December 2015. We collected information regarding clinical characteristics of enrolled children. Stool samples were obtained within 24 h of hospital admission and tested for rotavirus using rotavirus antigen detection enzyme immunoassay. Samples were sent to the regional reference laboratories in Australia and South Korea for genotyping. Bivariate analyses compared demographic and clinical characteristics between rotavirus positive and negative children using Chi-square statistical testing. Seasonality of rotavirus and annual genotype distribution are also described. RESULTS We enrolled 1853 children <5 years with acute gastroenteritis during the surveillance period and collected 1772 fecal specimens, 982 (55%) of which tested positive for rotavirus. A higher proportion of rotavirus acute gastroenteritis was observed among children 12-23 months of age as compared to rotavirus negative children in the same age group, 41% vs 36%. Eighty-six percent of rotavirus positive children experienced vomiting, as compared to 65% of rotavirus negative children. Eighty-five percent (n = 830/982) of rotavirus positive specimens occurred during the dry season (January-April). The most common genotypes identified were G1, G2, G3 and P8 and P4. The most prevalent combined genotype differed annually during the surveillance period. CONCLUSION Surveillance continues to be important in documenting the burden of rotavirus in children <5 years in Lao PDR as well as providing a baseline for determining the impact of rotavirus vaccine once it is introduced into Lao PDRs national immunization schedule.