Detection of noroviruses in tap water in Japan by means of a new method for concentrating enteric viruses in large volumes of freshwater

A virus concentration method using a cation-coated filter was developed for large-volume freshwater applications. Poliovirus type I (LSc 2ab Sabin strain) inoculated into 40 ml of MilliQ (ultrapure) water was adsorbed effectively to a negatively charged filter (Millipore HA, 0.45-mum pore size) coated with aluminum ions, 99% (range, 81 to 114%) of which were recovered by elution with 1.0 mM NaOH (pH 10.8) following an acid rinse with 0.5 mM H,SO, (pH 3.0). More than 80% poliovirus recovery yields were obtained from 500-ml, 1,000-ml, and 10-liter MilliQ water samples and from tap water samples. This method, followed by TaqMan PCR detection, was applied to determine the presence of noroviruses in tap water in Tokyo, Japan. In a 14-month survey, 4 (4.1%) and 7 (7.1%) of 98 tap water samples (100 to 532 liters) contained a detectable amount of noroviruses of genotype I and genotype 2, respectively. This method was proved to be useful for surveying the occurrence of enteric viruses, including noroviruses, in large volumes of freshwater.