Reduction of Tulane Virus (a Human Norovirus Surrogate) by Chlorine Dioxide (ClO2) Gas

Introduction: Human noroviruses (HNoV) are reportedly responsible for 400,000 emergency visits with $2 billion in financial losses yearly within the United States alone. Recently, Tulane virus (TV) has been used as a cultivable HNoV surrogate to determine effective inactivation strategies against HNoV. Chlorine dioxide (ClO₂) gas, a strong oxidizer has been used in water disinfection. The advantages of ClO₂ gas over solution include greater penetration ability that results in improved effectiveness. Recently, reduction of 3 log PFU/ml MNV-1 with 2.5 mg/L after 2 min and to non-detectable levels with 4 mg/L ClO₂  gas after 1 min were reported. Inactivation of TV by ClO₂ gas is unknown.

Purpose: The objective of this research was to determine the ability of ClO₂ gas to inactivate TV at room temperature (RT).

Methods: TV at ~6 log PFU was aseptically dried on sterile formica coupons and treated with 2.5 and 4 mg/L of ClO₂ gas for 30, 60, 120, and 300 s at ~75% relative humidity (RH) and RT. At each time point, TV was recovered using cell-culture media containing 10% fetal bovine serum. TV infectivity was assessed by plaque assays in duplicate using LLC-MK2 host cells. Data obtained from triplicate treatments were statistically analyzed.

Results: TV (~6 log PFU) was reduced by 1.16±0.25, 2.56±1.38, 3.37±1.67 log PFU and to non-detectable levels with 2.5 mg/L ClO₂ gas treatment after 30, 60, 120 and 300 s, respectively at ~75% RH and RT. Increased TV reduction of 3.36±1.77, 3.37±1.54, 4.59±1.13 log PFU and to non-detectable levels was obtained with 4 mg/L ClO₂gas treatment after 30, 60, 120 and 300 s, respectively, at ~75% RH and RT.

Significance: This study showed that ClO₂ gas treatments are effective in decreasing TV titers in a time- and concentration-dependent manner similar to MNV-1. Further studies on ClO₂ gas applications on produce are needed to prevent HNoV transmission/outbreaks.