Addressing Personal Protective Equipment (PPE) Decontamination: Methylene Blue and Light Inactivates SARS-CoV-2 on N95 Respirators and Masks with Maintenance of Integrity and Fit (preprint)

BackgroundThe coronavirus disease 2019 (COVID-19) pandemic has resulted in severe shortages of personal protective equipment (PPE) necessary to protect front-line healthcare personnel. These shortages underscore the urgent need for simple, efficient, and inexpensive methods to decontaminate SARS-CoV-2-exposed PPE enabling safe reuse of masks and respirators. Efficient decontamination must be available not only in low-resourced settings, but also in well-resourced settings affected by PPE shortages. Methylene blue (MB) photochemical treatment, hitherto with many clinical applications including those used to inactivate virus in plasma, presents a novel approach for widely applicable PPE decontamination. Dry heat (DH) treatment is another potential low-cost decontamination method. MethodsMB and light (MBL) and DH treatments were used to inactivate coronavirus on respirator and mask material. We tested three N95 filtering facepiece respirators (FFRs), two medical masks (MMs), and one cloth community mask (CM). FFR/MM/CM materials were inoculated with SARS-CoV-2 (a Betacoronavirus), murine hepatitis virus (MHV) (a Betacoronavirus), or porcine respiratory coronavirus (PRCV) (an Alphacoronavirus), and treated with 10 {micro}M MB followed by 50,000 lux of broad-spectrum light or 12,500 lux of red light for 30 minutes, or with 75{degrees}C DH for 60 minutes. In parallel, we tested respirator and mask integrity using several standard methods and compared to the FDA-authorized vaporized hydrogen peroxide plus ozone (VHP+O3) decontamination method. Intact FFRs/MMs/CM were subjected to five cycles of decontamination (5CD) to assess integrity using International Standardization Organization (ISO), American Society for Testing and Materials (ASTM) International, National Institute for Occupational Safety and Health (NIOSH), and Occupational Safety and Health Administration (OSHA) test methods. FindingsOverall, MBL robustly and consistently inactivated all three coronaviruses with at least a 4-log reduction. DH yielded similar results, with the exception of MHV, which was only reduced by 2-log after treatment. FFR/MM integrity was maintained for 5 cycles of MBL or DH treatment, whereas one FFR failed after 5 cycles of VHP+O3. Baseline performance for the CM was variable, but reduction of integrity was minimal. InterpretationMethylene blue with light and DH treatment decontaminated masks and respirators by inactivating three tested coronaviruses without compromising integrity through 5CD. MBL decontamination of masks is effective, low-cost and does not require specialized equipment, making it applicable in all-resource settings. These attractive features support the utilization and continued development of this novel PPE decontamination method.

Face Masks Against COVID-19: An Evidence Review (preprint)

The science around the use of masks by the general public to impede COVID-19 transmission is advancing rapidly. Policymakers need guidance on how masks should be used by the general population to combat the COVID-19 pandemic. In this narrative review, we develop an analytical framework to examine mask usage, considering and synthesizing the relevant literature to inform multiple areas: population impact; transmission characteristics; source control; PPE; sociological considerations; and implementation considerations. A primary route of transmission of COVID-19 is via respiratory droplets, and is known to be transmissible from presymptomatic and asymptomatic individuals. Reducing disease spread requires two things: first, limit contacts of infected individuals via physical distancing and other measures, and second, reduce the transmission probability per contact. The preponderance of evidence indicates that mask wearing reduces the transmissibility per contact by reducing transmission of infected droplets in both laboratory and clinical contexts. Public mask wearing is most effective at reducing spread of the virus when compliance is high. The decreased transmissibility could substantially reduce the death toll and economic impact while the cost of the intervention is low. Given the current shortages of medical masks we recommend the adoption of public cloth mask wearing, as an effective form of source control, in conjunction with existing hygiene, distancing, and contact tracing strategies. Because many respiratory droplets become smaller due to evaporation, we recommend increasing focus on a previously overlooked aspect of mask usage: mask-wearing by infectious people ("source control") with benefits at the population-level, rather than mask-wearing by susceptible people, such as health-care workers, with focus on individual outcomes. We recommend that public officials and governments strongly encourage the use of widespread face masks in public, including the use of appropriate regulation.

Is the fit of N95 facial masks effected by disinfection? A study of heat and UV disinfection methods using the OSHA protocol fit test. (preprint)

The current COVID-19 pandemic has highlighted global supply chain shortcomings in the US hospital delivery system, most notably personal protective equipment (PPE) and COVID-19 is found on these masks ~ 7 days. Recent work from our group has shown two promising disinfection methods for N95 facial masks, dry heat (hot air (75C, 30 min) and UVGI which is UVGI 254 nm, 8W, 30 min. Using N95 five models of N95 masks from three different manufacturers we determined the following: 1) Hot air treated N95 masks applied over 5 cycles did not degrade the fit of masks (1.5% change in fit factor, p = .67), 2) UVGI treated N95 masks applied over 10 cycles were significantly degraded in fit and did not pass quantitative fit testing using OSHA testing protocols on a human model (-77.4% change in fit factor, p = .0002).