Ultraviolet-C efficacy against human norovirus GII.4 and hepatitis A virus in groundwater

Abstract

This study investigated the inactivation kinetics of the human norovirus GII.4 (HuNV GII.4) and hepatitis A virus (HAV) in artificially inoculated groundwater under Ultraviolet-C irradiation (0-240 mWs/cm(2)). Viral genome copies were quantified using RT-qPCR and PMA/RT-qPCR to evaluate the effects of the UV-C dose and to distinguish potentially infectious particles. For HuNV GII.4, the number of genome copies decreased from 4.11 to 1.99 log(10) copies/mu L by RT-qPCR, and from 4.11 to 1.69 log(10) copies/mu L following PMA treatment. The effect for HAV was similar, with reductions from 4.89 to 1.51 log(10) copies/mu L (RT-qPCR) and to 1.06 log(10) copies/mu L (PMA/RT-qPCR). Data fitting with the Weibull model revealed significantly higher D-values for HuNV GII.4 (57.51 mWs/cm(2)) compared with HAV (15.99 mWs/cm(2)), indicating that HuNV GII.4 was approximately 3.6-fold more resistant to UV-C irradiation. The PMA/RT-qPCR data supported this trend, with D-values of 38.62 mWs/cm(2) for HuNV GII.4 and 11.12 mWs/cm(2) for HAV. Overall, HuNV GII.4 demonstrated greater resistance to UV-C irradiation than HAV across both molecular detection methods. PMA treatment improved the accuracy of the viability assessment by weakening the signals from non-infectious particles, thus underscoring its utility for evaluating disinfection efficacy in water environments.