Investigation of norovirus occurrence in groundwater in metropolitan Seoul, Korea.

Groundwater is an important source of drinking and household water worldwide. Hence, the quality of groundwater is very important for preventing waterborne disease outbreaks and should be properly monitored. This study investigated the prevalence of waterborne viruses and fecal indicators in groundwater in metropolitan Seoul and Gyeonggi province, South Korea. A total of 116 samples of groundwater were taken using NanoCeram filters during both summer (June to August) and fall-winter seasons (October to December) in 2008. Among 71 sampling sites, 28 (48.3%) and 18 (35.3%) were positive for norovirus (NoV) from the summer and fall-winter season, respectively. The identified genotypes of NoV include GI-1, 4, 8, 9 and GII-4, 10, 11 (or 17), 13, 15 (or 16). None of fecal indicators was significantly correlated with NoV in groundwater. Among the tested fecal indicators, somatic coliphage (95.3%) showed an excellent true-negative rate of NoV occurrence. The combination of chemical, microbial and viral indicators increased the positive predictive value (50-100%). This study demonstrated a high prevalence of NoV in groundwater in metropolitan Seoul areas and characterized the positive and negative predictive values of a fecal indicator for predicting NoV prevalence.