Of masks and methylene blue-The use of methylene blue photochemical treatment to decontaminate surgical masks contaminated with a tenacious small nonenveloped norovirus

Background: In the context of the SARS-CoV-2 pandemic, reuse of personal protective equipment, specifi-cally that of medical face coverings, has been recommended. The reuse of these typically single-use only items necessitates procedures to inactivate contaminating human respiratory and gastrointestinal patho-gens. We previously demonstrated decontamination of surgical masks and respirators contaminated with infectious SARS-CoV-2 and various animal coronaviruses via low concentration-and short exposure methy-lene blue photochemical treatment (10 mM methylene blue, 30 minutes of 12,500-lux red light or 50,000 lux white light exposure).Methods: Here, we describe the adaptation of this protocol to the decontamination of a more resistant, non -enveloped gastrointestinal virus and demonstrate efficient photodynamic inactivation of murine norovirus, a human norovirus surrogate.Results: Methylene blue photochemical treatment (100 mM methylene blue, 30 minutes of 12,500-lux red light exposure) of murine norovirus-contaminated masks reduced infectious viral titers by over four orders of magnitude on surgical mask surfaces.Discussion and Conclusions: Inactivation of a norovirus, the most difficult to inactivate of the respiratory and gastrointestinal human viruses, can predict the inactivation of any less resistant viral mask contaminant. The protocol developed here thus solidifies the position of methylene blue photochemical decontamination as an important tool in the package of practical pandemic preparedness.(c) 2022 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Automated summary

Methylene blue photochemical treatment can effectively reduce infectious viral titers of murine norovirus on contaminated masks, reinforcing the position of methylene blue photochemical decontamination as an important tool in practical pandemic preparedness.