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Transmission PreventionCopy Link!
This section addresses transmission prevention. Please see COVID overview for the causes of Infectivity and Transmission.
Literature Review (Infection Control): Gallery View, Grid View
Wearing Face Masks and ShieldsCopy Link!
Updated Date: December 19, 2020
Literature Review: Gallery View, Grid View
This section covers general public use of face masks and shields, for health care usage, see Personal Protective Equipment
Universal masking has been shown to reduce transmission. More data exist for medical settings, but the United States CDC and the WHO both recommend mask use in non-medical settings as well (CDC, WHO).
How do Face Masks Work?Copy Link!
- Face Masks provide a barrier against a high percentage of the viral particles released from a wearer’s mouth and nose (Ma et al).
- Wearing a medical mask has been demonstrated to result in a six-fold decrease in particle emission during breathing (Asadi et al). Systematic review of research literature on face masks shows that they reduce risk of infection by 85%, with greater effect noted in healthcare settings (MacIntyre et al). Even loose-fitting masks appear to block 51% of particles. (Brooks et al)
- Available evidence also indicates that face masks can protect the wearer from inhaling viral particles. Face masks with multiple layers of cloth containing higher thread counts are more effective (CDC).
- The effectiveness of masks may be different as new more transmissible viral variants with higher viral loads, such as Delta variant, emerge (Hetemäki et al). However, they are likely to retain some efficacy.
- Populations can more easily adhere to universal masking advice than stay-at-home orders in some settings. Face masks allow people to leave their homes for essential reasons with less risk to others.
Can Face Masks Harm People?Copy Link!
Face masks do not interfere with the exchange of oxygen or carbon dioxide, even in patients with severe lung impairment (Samannan et al). Depending on the face mask, it may change the rate of flow of air, which can make people feel uncomfortable, especially if they have obstructive lung disease that also impedes air flow, such as COPD or asthma. Wearing a medical mask can be uncomfortable, but will not cause oxygen deficiency or carbon dioxide intoxication. Make sure that face masks remain dry (WHO). CDC recommends face masks above age 2; WHO recommends against requiring face masks for children under the age of 5 (WHO).
Types of Face MaskCopy Link!
There are several major categories of face masks. In many places manufactured medical-grade face masks (surgical, KN95, and 95) are in short supply. If there is a shortage of medical-grade face masks, they should be reserved for healthcare workers, confirmed COVID-19 patients, patients with symptoms of COVID-19, or patients at high risk of complications (WHO). More details on different types of medical-grade masks are available in PPE Types and Uses.
Tool: Instructions on How to Make Your Own Face Mask.
Face Shields and GogglesCopy Link!
Face shields and goggles are meant to prevent droplets and sprays from entering the eyes (for example, when caring for a hospital patient or a sick family member at home).Regulatory guidance and standards on forms of eye protection are highly variable. For best protection, wear a face shield that fits snugly against the forehead and extends the full length of the face and to the point of each ear (Roberge).. There is lack of evidence to demonstrate that face shields alone are sufficient as a form of source control for protecting others (CDC). They are also not sufficient to protect the wearer when worn alone, and should generally be worn with a face mask (Roberge). When a face mask cannot be worn, a face shield can be worn instead but does not offer the same level of infection control (CDC).
When to Wear a Face MaskCopy Link!
- When leaving the house
- In quarantine/self-quarantine/isolation when contact with others is necessary
- In workplaces and on public transportation
- When entering someone else’s home to provide an essential service
- When indoors with people who do not belong to your household, including relatives
- When cleaning streets or disposing of domestic rubbish
- A face mask is suggested, but not absolutely necessary in some outdoor areas if a 2-meter distance can be kept from other people at all times. Consult local rules and regulations.
How to Use a Face MaskCopy Link!
- Wash your hands with soap and water or an alcohol-based hand sanitizer before putting on, touching, or removing a face mask (WHO). This prevents you from accidentally contaminating your face if you have coronavirus on your hands. Avoid touching the front of a face mask by touching the strings or ties instead.
- The face mask must be worn over both the mouth and the nose, it is not effective if used over the mouth alone. Tie securely to minimize gaps between face and mask.
- Avoid touching the face mask while wearing it. If you do, perform hand hygiene.
- When removing a face mask, undo the ties and carefully fold the face mask inside-out. Place directly in a designated area for disposal or washing, or in a plastic bag.
- Wash cloth face mask in soap or detergent, preferably with hot water. If hot water cannot be used, boil the mask for 1 minute after washing with detergent (WHO). Only use a cloth face mask that has been properly cleaned.
- If a face mask becomes damp or noticeably soiled, replace it immediately with a clean one.
Tool: WHO Infographics on How to Wear a Face Mask