In a comprehensive review, an international consortium of authors, of which Dr. Vladimír Ždímal of the Institute of Chemical Process Fundamentals of the CAS, aim to provide an insight into the utility of public usage of cloth masks in the COVID-19 pandemic. Since the primary route of transmission of the SARS-Cov-2 virus is by respiratory particles (droplets and aerosols), public mask-wearing was found to help reduce its spread efficiently, especially if compliance is high, i.e. when other public health measures such as social distancing are applied and respected.
The paper “An evidence review of face masks against COVID-19” published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) reviews relevant literature on public mask-wearing in the context of the COVID-19 pandemic, considering the current global shortage of surgical masks and N95/FFP2 respirators and the use of cloth masks that followed. Summarizing direct epidemiological evidence, ecological studies, modeling, randomized control trials, or studies of direct physical testing of respirators, surgical and cloth masks the review offers evidence that a generalized public mask-wearing in combination with complementary public health measures contributes to decreasing the Re to below 1, enabling its authors to recommend widespread nonmedical mask-wearing to reduce community spread of the SARS-Cov-2 virus.
Background
Widespread cloth mask use recommendation by Wu Lien Teh to control the 1910 Manchurian Plague is considered as a milestone in systematic disease control practice, although airborne transmission of plague was known as early as the 13th century and mouth coverings were used in the 14th century already. Cotton and silk were the most used materials; along with other materials such as chiffon or flannel, they were found recently to have filtration efficacy greater than 96% for particles larger than 0.3 μm.