The molecular epidemiology of norovirus infections was studied in food handlers without any symptoms from January to December 2015 in Busan city, Korea. A total of 2,174 fecal specimens from asymptomatic food handlers were analyzed, and 2.3% (49/2,174) were norovirus-positive. Fourteen of 335 samples (4.2%) were positive in January; fifteen of 299 samples (5.0%) in February, and seven of 189 samples (3.7%) in December. However, norovirus was rarely detected in other months. From sequencing analysis, 11 genotypes (five GI and six GII genotypes) were detected. Among the 42 capid gene sequences identified, 14 were from the GI genogroup, while 28 were from the GII genogroup. The most commonly detected genotype was GII.17, comprising 15 (35.7%) of positive samples. From January 2012 to December 2015, 5,138 samples were collected from gastroenteritis patients and outbreaks in Busan. The most detected genotype in 2012, 2013, and 2014 was GII.4 (121, 24, and 12 cases, respectively), but in 2015, GII.17 (25 cases) was the most common. The GII.4 genotype was the major cause of acute gastroenteritis from 2012 to 2014, but the GII.17 genotype became the most prevalent cause in 2015. Continued epidemiological surveillance of GII.17 is needed, together with assessment of the risk of norovirus infection.

This paper studies an infection of norovirus and astrovirus in outbreaks in Korea. In March 2016, gastroenteritis outbreaks occurred in Busan. 522 students of three departments at university D had meeting at a restaurant near the university. Some of them had symptom such as diarrhea, vomiting. Epidemiological, laboratory and environmental investigations were performed to identify the agents of the outbreaks. Fecal specimens were collected from 35 students and 7 food handlers to identify causative viral agents. Norovirus genogroup GI and GII were detected from diarrhea patients. Astrovirus was also detected from some of them. In particular, these outbreaks were the first occurrence associated with astrovirus in Busan. Total of 42 samples were collected, and 24 samples resulted in positive to norovirus (16 cases) and astrovirus (8 cases). To identify the molecular genetic information of norovirus, we carried out sequences analysis of the detected strains. Norovirus genotypes were classified into GI.3, GI.4, GII.4, GII.13, GII.17 and GII.21. Astrovirus genotypes were seven astrovirus type 5 and one astrovirus type 2. We performed environmental investigation about water at the kitchen, but norovirus and astrovirus were not detected. The statistical analysis was conducted to evaluate the association between illness and risk factors. The results of this study may contribute to accumulate more the epidemiological data and develop the public health and hygiene.

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