Health Department, CDC: Community use of masks works to control the spread of COVID-19
Published 5:09 pm Thursday, December 9, 2021
The following release is from the Stanly County Health Department:
On Monday, the Center for Disease Control and Prevention provided a science brief on the community use of masks to control the spread of SARS-CoV-2. At least 10 studies in several countries, including the United States, confirmed the benefit of universal masking in community level analysis. Experimental and epidemiologic data support community masking to reduce the spread of SARS-CoV-2, including alpha and delta variants, among adults and children. The prevention benefit of masking is derived from the combination of source control and wearer protection.
SARS-CoV-2 infection is transmitted predominantly by inhalation of respiratory droplets generated when people cough, sneeze, sing, talk, or breathe. Multi-layer cloth masks block release of exhaled respiratory particles into the environment, along with any microorganisms associated with these particles. Cloth masks not only effectively block most large droplets (i.e., 20-30 microns and larger), but they can also block the exhalation of fine droplets and particles (also often referred to as aerosols) smaller than 10 microns which increase in number with the volume of speech and specific types of phonation. Multi-layer cloth masks can both block 50-70 percent of these fine droplets and particles and limit the forward spread of those that are not captured. Upwards of 80 percent blockage has been achieved in human experiments, with cloth masks in some studies performing on par with surgical masks as barriers for source control.
Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns. The relative filtration effectiveness of various masks has varied widely across studies, in large part due to variation in experimental design and particle sizes analyzed. Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50 percent of fine particles less than 1 micron.
Research also supports that under most circumstances, mask wearing has no significant adverse health effects for wearers. Studies of healthy hospital workers, older adults, and adults with chronic obstructive pulmonary disease (COPD) reported no to minimal changes in oxygen or carbon dioxide levels while wearing a cloth or surgical mask either during rest or moderate physical activity. Additionally, a study of 60 elementary school children reported no adverse cardiovascular (e.g., heart rate) or pulmonary (e.g., peripheral oxygen saturation) effects among children while wearing a cloth face covering in a classroom for 30 consecutive minutes of instructional time. A separate study observed no oxygen desaturation or respiratory distress after 60 minutes of monitoring among children less than 2 years of age when masked during normal play. A randomized trial among 40 children aged 3-10 years old scheduled for elective surgery, found that protective surgical face masks could be used safely in the postoperative period. In a prospective school-based cohort study of children aged 10-17 years who wore masks for 6-7 hours during the school day, some children self-reported general (4-7 percent) or situation-specific (2-4 percent) side-effects such as skin irritation, headache or difficulty breathing during physical education.