Adopting Who Guidance on Fabric Masks for COVID-19

Abstract

On June 5, 2020, the World Health Organization (WHO) released updated guidance on the design and use of fabric masks for COVID-19. This Commentary discusses the new guidance on non-medical fabric masks as supplementary risk reduction strategies alongside physical distancing and hand hygiene, highlighting key differences from earlier Centers for Disease Control (CDC) guidelines. Notably, while the CDC recommended cotton masks with at least two layers, the WHO now recommends masks with at least three layers including a hydrophilic inner layer (e.g., cotton) to retain droplets and hydrophobic synthetic outer layers (e.g., spunbond nonwoven polypropylene, NWPP) to enhance filtration and reduce penetration of external contaminants through the mask. This key change is supplemented with additional guidance to assist mask users and makers in choosing materials with a balance of breathability and filtration performance. Cotton masks made according to the earlier CDC guidance can be adapted to comply with the WHO update by adding a single layer spunbond NWPP mask cover.