Persistence of SARS-Co-V-2 on N95 filtering facepiece respirators: implications for reuse

In response to the shortage of N95 filtering facepiece respirators for healthcare workers during the COVID-19 pandemic, the Centers for Disease Control and Prevention issued guidance for extended use and limited reuse of N95 FFRs to conserve supply. Previously worn N95 filtering facepiece respirators can serve as a source of pathogens, which can be transferred to the wearer while doffing and donning a respirator when practicing reuse. When practicing limited filtering facepiece respirators reuse, to reduce the risk of self-contamination, the Centers for Disease Control and Prevention recommends storing filtering facepiece respirators for five days between uses to allow for the decay of viable pathogens including SARS-CoV-2. This study assesses the persistence of the SARS-CoV-2 strain USA-WA1/2020 on N95 filtering facepiece respirators under controlled storage conditions for up to 5 days to inform the Centers for Disease Control and Prevention guidance. Coupons excised from six N95 filtering facepiece respirator models and glass slide coverslips were inoculated with the virus in a defined culture medium and in human saliva and stored at 20 °C and 20%, 45%, and 75% relative humidity. Statistically significant differences in SARS-CoV-2 half-lives were measured among the tested humidity levels with half-lives decreasing from an average of approximately 30 hr at 20% relative humidity to approximately 2 hr at 75% relative humidity. Significant differences in virus half-lives were also observed between the culture medium and saliva suspension media at 20% and 45% relative humidity with half lives up to 2.9 times greater when the virus was suspended in cell culture medium. The 5-day storage strategy, assessed in this study, resulted in a minimum of 93.4% reduction in viable virus for the most challenging condition (20% relative humidity, cell culture medium) and exceeding 99% reduction in virus at all other conditions.