Ahyong Jeong

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.

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).

Seasonal Prevalence of Asymptomatic Norovirus Infection in Korean Children

The prevalence of asymptomatic norovirus (NoV) infection was investigated in children registered for kindergarten in Korea during the winter and summer. Children with no gastrointestinal symptoms, including diarrhea and abdominal pain, during the 2 weeks before and following sample collection were included in this investigation. NoV presence and genetic identification were determined with real-time reverse transcriptase-polymerase chain reaction and conventional nested reverse transcriptase-polymerase chain reaction. The prevalence of NoV in asymptomatic children was 5.5% in the winter and 3.5% in the summer, respectively. GII.4 was the most prevalent NoV genotype, but GII.2 and GI.10 were also found during genetic analysis. This study demonstrates that asymptomatic NoV infection may be an important source of transmission in kindergarten children.

Epidemiology of astrovirus infection in children.

Human astrovirus (HAstV) is a major cause of acute diarrhea among children, resulting in outbreaks of diarrhea and occasionally hospitalization. Improved surveillance and application of sensitive molecular diagnostics have further defined the impact of HAstV infections in children. These studies have shown that HAstV infections are clinically milder (diarrhea, vomiting, fever) than infections with other enteric agents. Among the 8 serotypes of HAstV identified, serotype 1 is the predominant strain worldwide. In addition to serotype 1, the detection rate of HAstV types 2 to 8 has increased by using newly developed assays. HAstV is less common compared with other major gastroenteritis viruses, including norovirus and rotavirus; however, it is a potentially important viral etiological agent with a significant role in acute gastroenteritis. A better understanding of the molecular epidemiology and characteristics of HAstV strains may be valuable to develop specific prevention strategies.

Seroepidemiology of Predominant Norovirus Strains Circulating in Korea by Using Recombinant Virus-Like Particle Antigens

An epidemiological survey on human norovirus (NoV)-associated gastroenteritis was conducted to clarify the prevalence of NoV infections in children and adults in Korea. Recombinant capsid proteins from three major NoV genotypes (GI-4, GII-3, and GII-4) were expressed using a baculovirus expression system, and the morphology and antigenicity of self-assembled virus-like particles were then confirmed by electron microscopy and Western blotting with a NoV-specific antibody. To determine seroprevalence, an enzyme-linked immunosorbent assay was performed to detect antibodies against virus-like particles antigen in 346 serum specimens collected from persons who visited five public heath care centers for regular physical examination in Jeollanam-do, Korea, between 2005 and 2006. The seroprevalence of immunoglobulin G antibodies against the GI-4, GII-3, and GII-4 NoV genotypes was 84.1%, 76.3%, and 94.5%, respectively. A rapid decrease in seroprevalence occurred after birth, with the lowest levels observed in the <23-month age group, and a steep increase in seroprevalence occurred in early childhood, reaching 60.5% for GI-4, 65.1% for GII-3, and 90.7% for GII-4 at age 2-5 years, and over 80% for all three genotypes in subjects aged 20 years or older. The seroprevalence of different NoV genotypes statistically differed across the age groups (p<0.01).