By Mary Hearty

The World Health Organization (WHO) advices on the use of masks as part of a comprehensive package of prevention and control measures to limit the spread SARS-CoV-2, the virus that causes COVID-19.

Depending on the type, masks can be used either for protection of healthy persons or to prevent onward transmission by an infected person. This is through reduction of spread of respiratory droplets containing infectious viral particles, including from infected persons before they develop symptoms.

Mask use by healthy people reduces stigmatization and increases acceptance by people caring for patients with COVID-19 in non-clinical settings.

Again, use of mask by healthy people makes them feel they can play a role in contributing to stopping the spread of the virus. Furthermore, it helps in preventing transmission of other respiratory illnesses like tuberculosis and influenza and reducing the burden of those diseases during the pandemic.

Anyone suspected or confirmed of having COVID-19 or awaiting viral laboratory test results should wear a medical mask when in the presence of others.

Mask use in healthcare settings

WHO continues to recommend that health workers providing care to suspected or confirmed patients with COVID-19 wear specific types of mask, in addition to personal protective equipment that are part of standard, droplet and contact precautions.

“Wear medical mask in the absence of aerosol generating procedures (AGPs); respirator N95 or FFP2 or FFP3 standards, or equivalent in care settings for COVID-19 patients where AGPs are performed,” WHO instructs.

Also, these may be used by health workers when providing care to COVID-19 patients in other settings if they are widely available and if cost is not an issue.

In areas of known or suspected community or cluster SARS-CoV-2 transmission WHO advises universal masking for all persons within the health facility including primary, secondary and tertiary care levels, that is, outpatient care, and long-term care facilities.

Additionally, masks must be worn by inpatients when physical distancing of at least one metre cannot be maintained or when patients are outside of their care areas.

In areas of known or suspected sporadic SARS-CoV-2 transmission, health workers working in clinical areas where patients are present should continuously wear a medical mask. Besides, Exhalation valves on respirators are discouraged as they bypass the filtration function for exhaled air by the wearer.

Mask use in community settings

In areas of known or suspected community or cluster SARS-CoV-2 transmission, the general public is encouraged to wear non-medical masks during indoor, for instance, shops, shared workplaces, and schools, and outdoor settings where physical distancing of at least one metre cannot be maintained.

If indoors, unless ventilation has been be assessed to be adequate, WHO directs that the general public should wear a non-medical mask, regardless of whether physical distancing of at least one metre can be maintained.

Whereas, individuals with higher risk of severe complications from COVID-19, that is, people above 60 years old and those with underlying conditions such as cardiovascular disease or diabetes mellitus, chronic lung disease, cancer, cerebrovascular disease or immunosuppression, should wear medical masks when physical distancing of at least one metre cannot be maintained.

In any transmission scenarios like caregivers or those sharing living space with people with suspected or confirmed COVID-19, regardless of symptoms, should wear a medical mask when in the same room.

WHO encourages law makers to implement a risk-based approach when considering the use of masks for the general public.

Mask use in children

WHO recommends that children aged up to 5 years should not wear masks for source control. While for children between six and 11 years of age, a risk based-approach should be applied to the decision to use mask.

This risk-based approach include intensity of SARS-CoV-2 transmission, child’s capacity to comply with the appropriate use of masks and availability of appropriate adult supervision, local social and cultural environment, and specific settings such as households with elderly relatives, or schools.

Mask use also applies to children and adolescents 12 years or older. However, special considerations are required for immune-compromised children or for pediatric patients with cystic fibrosis or certain other diseases like cancer, as well as for children of any age with developmental disorders, disabilities or other specific health conditions that might interfere with mask wearing.

Mask use in home-based care patients with COVID-19

For patients with confirmed and suspected COVID-19 at home when care in a health facility or other residential setting is not possible, WHO advices on wearing a medical mask as much as possible.

This applies especially when there is no alternative to being in the same room with other people. The mask should also be changed at least once daily.

Persons who cannot tolerate a medical mask should rigorously apply respiratory hygiene, that is, cover mouth and nose with a disposable paper tissue when coughing or sneezing and dispose of it immediately after use or use a bent elbow procedure and then perform hand hygiene.

On the other hand, caregivers of or those sharing living space with people with suspected COVID-19 or with mild COVID-19 symptoms should wear a medical mask when in the same room as the affected person.

Mask use during physical activity

According to WHO, there are limited studies on the benefits and harms of wearing medical masks, respirators and non-medical masks while exercising.

The most significant impacts have been consistently associated with the use of respirators and in persons with underlying obstructive airway pulmonary diseases such as asthma and chronic obstructive pulmonary disease, especially when the condition is moderate to severe.

A recent review found negligible evidence of negative effects of mask use during exercise but noted concern for individuals with severe cardiopulmonary disease.

Therefore, WHO advises that people should not wear masks during vigorous intensity physical activity because masks may reduce the ability to breathe comfortably.

If the activity takes place indoors, adequate ventilation should be ensured at all times through natural ventilation or a properly functioning or maintained ventilation system. If all those measures cannot be ensured, consider temporary closure of public indoor exercise facilities like gyms.

Face shields for the general public

Face shields are considered to provide a level of eye protection only and should not be considered as an equivalent to masks with respect to respiratory droplet protection or source control.

In situations where mask is not available or an individual finds it difficult to wear a non-medical mask, for instance, persons with cognitive, respiratory or hearing impairments, face shields may be considered as an alternative, noting that they are inferior to masks with respect to droplet transmission and prevention.

Mask policies for the public

Policy makers are also recommended to clearly communicate the purpose of wearing a mask, including when, where, how, and what type of mask should be worn.

They should also explain what wearing a mask may achieve and what it will not achieve; and communicate clearly that this is one part of a package of measures along with hand hygiene, physical distancing, respiratory etiquette, adequate ventilation in indoor settings and other measures that are all necessary and all reinforce each other.