Antiviral Effect of Neutral Electrolyzed Water against Human Norovirus

Introduction: Human norovirus can persist in the environment for weeks, and contaminated surfaces often serve as reservoirs for its transmission. Many conventional sanitizers and disinfectants have shown poor efficacy against this virus, and there is a need for validation of novel products with higher efficacy. 

Purpose: To evaluate the anti-noroviral activity of neutral electrolyzed water (NEW) in both suspension and on surfaces. 

Methods: NEW was generated using a Mini-UL-75a device (Clarentis Technologies, Palm Beach Gardens, FL). Human norovirus GII.4 Sydney 20% fecal suspensions (with and without an additional 5% organic load) were used as inoculum. Suspension assays (ASTM method E1052-11) were performed using NEW at concentrations of 50, 150, and 250 ppm free available chlorine (FAC, pH 7) with a 1-min contact time. Carrier tests (ASTM method E1053-11) were done using inoculated stainless steel coupons exposed to NEW (250 ppm FAC, pH 7) for 10, 15, and 30 min. Log reduction of norovirus genomic copy number as a function of NEW exposure was determined using RT-qPCR with and without prior RNase treatment. 

Results: In suspension assay, NEW (250 ppm FAC, pH 7) produced a 4.8 ± 0.6 log GII.4 genome copy number reduction. An additional 5% organic load significantly reduced NEW efficacy, as evidenced by log reduction of 1.9 ± 0.2 (P<0.05). For surface tests, NEW (250 ppm FAC, pH 7) produced a 1.6 ± 0.7, 2.4 ± 0.5, and 5.0 ± 0.5 log reduction after 10, 15, and 30 min, respectively (P<0.05). Anti-noroviral efficacy decreased significantly to <0.2 log genomic copies in the presence of 5% higher organic load regardless of the contact time (P<0.05). 

Significance: Under the parameters of this study, NEW shows promise as an alternative surface disinfectant when used at 250 ppm on clean surfaces for a contact period of 15-30 min.