Inactivation of Human Norovirus and Feline Calicivirus by Chlorine Dioxide Delivered as a Fog

Introduction: Human norovirus is the major cause of gastroenteritis in humans worldwide, responsible for 48% of foodborne illnesses in the United States. Contact surfaces can harbor norovirus through exposure to the stool or vomit of an infected person, and transmit the virus to humans and food. Proper surface disinfection can prevent virus transmission, and reduce the burden of illness associated with outbreaks.

Purpose: To investigate the inactivation of representative human norovirus GI.6 and GII.4 Sydney strains, and the cultivable surrogate feline calicivirus (FCV), by chlorine dioxide delivered as a fog.

Methods: Virus stocks were dried on stainless steel coupons, and placed at five locations (different elevations and distances) in a 2,377 ft³ BSL-3 containment laboratory. Using the Room Decontamination System (RDS) 3110 (AeroClave™, Winter Park, FL), chlorine dioxide (Vital Oxide, West Palm Beach, FL) was aerosolized in the room at 12.4 ppm (0.35 ml/ft³, recommended) and 15.9 ppm (0.45 ml/ft³). After a 10 min dwell time, viruses were recovered by elution, and log reductions in human norovirus and FCV were calculated based on genomic copies (after RNase pre-treatment) and plaque forming units, respectively. Results were expressed as log reduction in estimated virus concentration after treatment.

Results: For a treatment with 12.4 ppm chlorine dioxide delivered as a fog, 1.7 ± 0.2 and 0.5 ± 0.0 log reductions were observed for human norovirus GI and GII, respectively (P<0.05). At 15.9 ppm, log reduction was only 0.4 ± 0.1 for both GI and GII strains. Log reduction in infectious FCV was 2.4 ± 0.2 at 12.4 ppm versus 1.8 ± 0.1 at 15.9 ppm (P=0.007). Activity against all three viruses was uniform across various room locations.

Significance: Chlorine dioxide delivered as a fog demonstrated marginal activity against human norovirus and FCV under the parameters used in this study.