Virucidal Efficacy of Gaseous Ozone Against Type 1 Herpes Simplex Virus (HSV-1)

Viruses represent a major threat to human health and are capable of spreading either via direct exposure or contamination of inanimate surfaces. Certain viruses have been shown to remain viable on surfaces of dental implants and devices, fabrics and on plastics for hours, days and weeks representing a source of continuous viral transmission which must be mitigated. In this study, we compared the effect of varying concentrations of gaseous ozone (40, 20, 10, 5, and 1 ppm) on Herpes Simplex Virus (HSV-1) coated on the surfaces of clear polystyrene tissue culture (TC) plates and stainless-steel disc at varying time intervals (1.5, 3, 6, and 8 h) at >90% relative humidity and at 21–25 ˙C (±2˙C). Test samples were placed at a height of 1 and 1.5 m from ozone source. Viral viability after ozone exposure was determined using Vero cells and the viral titer was quantified using the Spearman–Karber’s method. Overall, inactivation of HSV-1 was dependent on ozone concentration and the duration of exposure. At 20 and 40 ppm, ozone rapidly depleted virus viability after 6 h. At 5 and 10 ppm a time-dependent reduction in viral infectivity was observed. At 10 ppm, viral titer decreased from approximately 5.2 pfu/mL at T = 0 to 3.5 and 2.1 pfu/mL after 1.5- and 6-h exposure on plastic surfaces. Similarly, viral titer decreased from approximately 5.6 pfu/mL at T = 0 to 3.0 to 2.0 pfu/mL at same time frame on steel surfaces. This study builds on earlier research in the field and demonstrates the ability of gaseous ozone to inactivate HSV-1 on two surfaces commonly found in food, medical and dental settings. This study recommends that further work is completed to identify optimum ozone, humidity, and temperature combinations to inactivate such viruses on surfaces found within these environments.