Epidemiological Study of Ground-waterborne Norovirus GI.3-associated Gastroenteritis Outbreaks in Gyeonggi Province of South Korea in May 2011

In May 2011, five consecutive gastroenteritis outbreaks were reported at schools in Gyeonggi-do. Epidemiological inspection revealed that one food manufacture company provided 'Kimchi', a traditional Korean side-dish, to these five schools for catering services. Fecal specimens were collected from students and food-handlers to determine causative viral agents. Norovirus genogroup GI was detected from 58 samples out of total 239 specimens by reverse-transcription (RT)-PCR, whereas norovirus GII was found only from one sample. Epidemiological studies also revealed that the Kimchi was processed using groundwater in the food manufacture company. Four groundwater samples were collected from the company and around the area. Norovirus GI was detected from three samples. To determine the norovirus genotypes of positive specimens from clinical and groundwater samples, sequencing and phylogenetic analyses were performed. The genogroup GI from 58 clinical and three groundwater samples and the GII from one food-handler were identified as norovirus GI.3 and GII.18, respectively. Sequence alignment analysis with norovirus GI.3 isolates revealed that identity between clinical and groundwater samples was over than 99.1% in nucleotide level. In conclusion, norovirus GI.3-contaminated groundwater caused the gastroenteritis outbreaks of five schools, through Kimchi. This molecular epidemiological study was an important report in Korea that clearly identified all transmission routes of norovirus GI.3.