What is WHO’s view on masks?
WHO recognizes that there are many questions about the use of face masks to prevent the transmission of COVID-19 in the community, and that many countries are recommending that people wear them. Wearing a medical mask can limit the spread of certain respiratory viral diseases, including COVID-19. However, the use of a mask alone is not sufficient to provide an adequate level of protection. Other measures such as physical distancing and hand hygiene should be adopted.
What is WHO recommending to countries that are considering public mask use in community?
For countries that are currently considering the use of masks, WHO advises decision makers to apply a risk-based approach and consider the following:
Purpose of mask use: if the intention is preventing the wearer transmitting infection to others (that is source control) or to offer protection to the wearer against infection (that is prevention).
Risk of exposure to COVID-19
- due to epidemiology/number of cases in the population: if there is high community transmission and other measures such as contact tracing or ability to carry out testing are not possible.
- due to epidemiology/number of cases in the population: if there is high community transmission and other measures such as contact tracing or ability to carry out testing are not possible.
- depending on occupation: e.g., individuals working in close contact with public (e.g., community health worker, cashier).
Vulnerability of the mask wearer/population: for example, if supplies are adequate medical masks could be used by people with comorbidities, such as cardiovascular disease or diabetes mellitus, older people, immunocompromised patients.
Setting in which the population lives: settings with high population density (e.g. refugee camps, those living in cramped conditions) and settings where individuals are unable to keep a safe distance (e.g. crowded buses or other transport).
Feasibility: availability and costs of masks, access to clean water to wash non-medical masks, and ability of mask wearers to tolerate adverse effects of wearing a mask.
Type of mask: medical mask versus non-medical mask (prioritization of medical masks for health care providers, symptomatic people and their caregivers).
In addition to these factors, potential advantages of the use of masks by healthy people in the community setting include reducing potential exposure risk from an infected person during the ‘pre-symptomatic’ period or if an infected person is asymptomatic.
There are potential risks and disadvantages that should be taken into account in any decision-making process on the use of masks:
- Non-medical or cloth masks could increase potential for COVID-19 to infect a person if the mask is contaminated by dirty hands and touched often, or kept on other parts of the face or head and then placed back over the mouth and nose
- Non-medical or cloth masks could increase potential for COVID-19 to infect a person if the mask is contaminated by dirty hands and touched often, or kept on other parts of the face or head and then placed back over the mouth and nose
- Depending on the type of mask used, could cause difficulty in breathing
- They can lead to facial skin breakdown
- They can lead to difficulty with communicating clearly
- They can be uncomfortable to wear
- It is possible that mask use, with unclear benefits, could create a false sense of security in the wearer, leading to diminished practice of recognized beneficial preventive measures such as physical distancing and hand hygiene.
What are non-medical masks and what is their use?
Non-medical masks are often homemade of breathable fabrics and can be commercially available as well. There are numerous designs for fabric masks, but they generally cover the nose and mouth, are secured with ties or elastic loops, include multiple layers of fabric, and can sometimes be washed and re-used.
The evidence about the benefits of these masks is limited. One good quality study showed that the risk of respiratory infection is increased (and not reduced) in health care workers using cotton cloth masks when compared to medical masks.
Cloth masks are currently being recommended by some countries as a means of source control in the general population. Although their protective effectiveness to the wearer is unknown, they may protect others if the wearer is a pre-symptomatic or asymptomatic carrier.
WHO is continuing to gather and review data as new studies become available and will update guidance accordingly.