Inactivation and UV Disinfection of Murine Norovirus with TiO ₂ under Various Environmental Conditions

Abstract

We studied inactivation and UV disinfection of murine norovirus (MNV) as a surrogate for human norovirus. We investigated the effects of different surface characteristics, temperatures, and NaCl concentrations on MNV survival using both a plaque assay and a real-time TaqMan reverse transcription (RT)-PCR assay. MNV survived more than 40 days on diaper material, on gauze, and in a stool suspension. Compared to inactivation at lower temperatures (-20 and 4 degrees C), inactivation of MNV was greater at higher temperatures (18 and 30 degrees C). On the surface of both gauze and diaper material, there was a <2-log(10) reduction in the amount of infectious MNV in 40 days after incubation at both -20 and 4 degrees C, compared to a >5-log(10) reduction after incubation at 30 degrees C in 24 days. MNV survived better in a stool suspension than on the surface of gauze or diaper material. A higher salt concentration increased the rate of inactivation of MNV. In 72 h, <0.3-, 1.5-, and 2.5-log(10) reductions in the amount of infectious MNV occurred in distilled water and 0.5 and 1 M NaCl, respectively. We observed only minor reductions in the numbers of viral RNA copies as quantified by real-time TaqMan RT-PCR regardless of the temperature, the salt concentration, or the suspending medium. We also evaluated UV disinfection of infectious MNV with and without TiO(2). The amount of MNV was significantly reduced by 254-nm UV with and without TiO(2). When 25 mJ/cm(2) UV was used, 3.3- and 3.6-log(10) reductions in the amounts of infectious MNV occurred with and without TiO(2), respectively. Our results demonstrate that MNV can persist in various environmental conditions and can be efficiently controlled by UV disinfection.