Source control (respiratory disease)
Source control is a strategy for reducing disease transmission by blocking
Mechanisms
Infections in general may spread by direct contact (for example, shaking hands or kissing), by inhaling
Coughs and sneezes can spread airborne droplets up to ~8 meters (26 ft). Speaking can spread droplets up to ~2 meters (6.6 ft).[6] It may be difficult to maintain these distances. For a masked person, or even one sneezing or coughing into a tissue or elbow, these distances are reduced.[8]
Masking any person who may be a source of infectious droplets (or aerosols) thus reduces the unsafe range of physical distances. If a person can be infectious before they are symptomatic and diagnosed, then people who do not yet know if they are infectious may also be a source of infection.
Handwashing helps to protect people against contact transmission, and against indirect droplet transmission. Handwashing removes infectious droplets that their mask caught (from either side) and which transferred to their hands when they touched their mask.[6]
For pathogens transmitted through the air, strategies to block cough air jets and to capture aerosols, e.g. the "Shield & Sink" approach, can be highly effective in minimizing exposure to respiratory secretions.[5]
Contrast with personal protective equipment
While source control protects others from transmission arising from the wearer, personal protective equipment protects the wearer themselves.[9] Cloth face masks can be used for source control but are not considered personal protective equipment[1][9] as they have low filter efficiency (generally varying between 2–60%), although they are easy to obtain and reusable after washing.[3][10] There are no standards or regulation for self-made cloth face masks.[3]
Type | Source control | Inhaled air filtration | Ref |
---|---|---|---|
Cloth face mask | Some | Bad | [1][3][9] |
Surgical mask or procedure mask | Good | Bad | [4][11] |
Respirator without exhalation valve | Good | Good | [4] |
Respirator with unfiltered exhalation valve | Bad | Good | [4] |
Respirator with filtered exhalation valve | Good | Good | [4] |
COVID-19 pandemic
During the COVID-19 pandemic, cloth face masks for source control have been recommended by the U.S. Centers for Disease Control and Prevention (CDC) for members of the public who leave their homes, and health care facilities are commended to consider requiring face masks for all people who enter the facility. Health care personnel and patients with COVID-19 symptoms are recommended to use surgical masks if available, as they are more protective.[15] Masking patients reduces the personal protective equipment recommended by CDC for health care personnel under crisis shortage conditions.[16]
The World Health Organization and European Centre for Disease Prevention and Control recommend face masks in non-healthcare community settings in severe epidemic situations with a high prevalence of asymptomatic but infectious persons, especially when visiting crowded indoor spaces such as grocery stores, public transportation, and for certain workers who must come into physical proximity with many other people.[3]
References
- ^ a b c "FAQs on the Emergency Use Authorization for Face Masks (Non-Surgical)". U.S. Food and Drug Administration. 2020-04-26. Retrieved 2020-05-21.
- PMID 32753296.
- ^ a b c d e f "Using face masks in the community - Reducing COVID-19 transmission from potentially asymptomatic or pre-symptomatic people through the use of face masks". European Centre for Disease Prevention and Control. 2020-04-08. Retrieved 2020-05-21.
- ^ a b c d e f g "Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings". U.S. Centers for Disease Control and Prevention. 2020-05-18. Retrieved 2020-05-21.
- ^ medRxiv 10.1101/2020.12.08.20233056v1.
- ^ PMID 32631450.
- PMID 33422679.
- on Wikimedia Commons)
- ^ a b c "Meat and Poultry Processing Workers and Employers: Interim Guidance from CDC and the Occupational Safety and Health Administration (OSHA)". Centers for Disease Control and Prevention. 2020-05-12. At section "Cloth face coverings in meat and poultry processing facilities". Retrieved 2020-05-24.
- PMID 20584862.
The results showed that cloth masks and other fabric materials tested in the study had 40–90% instantaneous penetration levels against polydisperse NaCl aerosols employed in the National Institute for Occupational Safety and Health particulate respirator test protocol at 5.5 cm s−1.
- ^ a b "N95 Respirators and Surgical Masks (Face Masks)". U.S. Food and Drug Administration. 2020-04-05. Retrieved 2020-05-23.
- ^ Robertson, Paddy (15 March 2020). "Comparison of Mask Standards, Ratings, and Filtration Effectiveness". Smart Air Filters.
- ^ 中华人民共和国医药行业标准:YY 0469–2011 医用外科口罩 (Surgical mask) (in Chinese)
- ^ 中华人民共和国医药行业标准:YY/T 0969–2013 一次性使用医用口罩 (Single-use medical face mask) Archived 2021-02-25 at the Wayback Machine (in Chinese)
- ^ "Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings". U.S. Centers for Disease Control and Prevention. 2020-05-18. Retrieved 2020-05-21.
- ^ "Strategies for Optimizing the Supply of N95 Respirators". U.S. Centers for Disease Control and Prevention. 2020-04-02. At section "Prioritize the use of N95 respirators and facemasks by activity type". Retrieved 2020-05-21.