Research on the contamination level of NoV and the combined water treatment system

Abstract

Noroviruses (NoVs) are the most important viruses that cause nonbacterial acute gastroenteritis in humans. One of the virulence factors of NoV, the great genetic diversity attributed to point mutations and recombinations, has brought forth the result of significant changes in the circulating NoV genotype patterns. In recognition of the necessity for tracking and monitoring of genetic diversity, a novel NoV variant was isolated from a patient in South Korea. To further understand its genetic characteristics and taxonomical classification, its genome was completely sequenced. Complete genome sequence analysis revealed three predicted ORFs

ORF1 (5,100 bp), ORF2 (1,623 bp), and ORF3 (807 bp). Comparative phylogenetic analysis of complete genome sequence of the isolated NoV strain showed that it may be in the Cluster I. Furthermore, subsequent phylogenetic analyses of three ORFs substantiated that this strain belongs to Cluster I/2006b. Therefore, the isolated NoV strain designated NoV Hu/GII-4/CUK-3/2008/KR. To investigate the contamination levels of NoVs in groundwater used at food catering facilities in South Korea, 1,090 groundwater samples were collected from Gyeonggi, Chungcheong, Gangwon, Gyeongsang, Jeolla and Jeju provinces and NoVs were detected in seven samples (three GII-4, two GII-17, one GII-3 and one GI-6) using the method based on the guidelines for NoVs Detection in Groundwater (Korea Food and Drug Association, KFDA), suggesting that NoVs are present in the groundwater of South Korea. Therefore, NoV reduction system is urgently required. To develop the water treatment system, electropositive filters were tested and 3M filter was selected due to its high fidelity of human NoV reduction in water. Using this 3M filter, the combined water treatment system was developed, consisting of electropositive filtration, UV irradiation, and chlorine disinfection. To evaluate this system, spiking samples containing >105 copies of human NoV particles were used and quantitative real-time RT-PCR using the eluted sample showed that no human NoV particle was detected in the samples, suggesting that this system indeed work for human NoV reduction in water. Therefore, this combined water treatment system should be used for human NoV reduction from the groundwater.