TORONTO -- The World Health Organization (WHO) has issued new guidelines for face masks amid the COVID-19 pandemic, suggesting that they be used in more situations than previously advised.

Chief among the new recommendations is that anyone living in an area where virus transmission is widespread should be encouraged to wear a non-medical mask when they are in a situation where physical distancing is difficult, such as on public transit, in stores and at places of worship and other mass gatherings.

Until the recommendations were released Friday, the WHO had not provided any guidance for or against the use of non-medical masks, saying there was not enough scientific evidence to determine if they could be helpful.

Some countries, including Canada, had nonetheless suggested that their citizens wear non-medical masks in certain scenarios without waiting for the WHO's guidance. The Public Health Agency of Canada has said for over a month that Canadians can help reduce the spread of their own respiratory droplets, which could potentially infect others, by wearing non-medical masks, and chief public health officer Dr. Theresa Tam said May 20 that non-medical masks should be worn when physical distancing cannot be achieved.

WHO Director-General Tedros Adhanom Ghebreyesus said Friday at a press briefing that the change in advice was "based on evolving evidence." One study recently found that homemade cloth masks may help provide a "modest reduction in transmission."

According to the WHO, advantages to encouraging citizens to wear non-medical masks include reducing the risk of asymptomatic carriers spreading the virus and reminding the population that the pandemic is ongoing and everyone can play a role in stopping it, as well as stimulating economic activity by "encouraging the public to create their own fabric masks."

Disadvantages include the risk of self-contamination from touching the mask too often or not cleaning it often enough, the potential that wearing a mask will lead to headaches, breathing difficulties or skin irritations, and the possibility of creating a false sense of security, as non-medical masks do not fully protect those wearing them.

"I cannot say this clearly enough: masks alone will not protect you from COVID-19," Tedros told reporters.

"Masks are not a replacement for physical distancing, hand hygiene and other public health measures."


In addition to the new guidelines for those not showing symptoms and unable to practise physical distancing, the WHO has updated its advice for medical professionals and some of those most at risk of developing severe complications should they contract COVID-19.

Medical masks have long been recommended for any health-care workers treating confirmed or suspected COVID-19 patients. Now, the WHO says anyone working in a clinical setting in an area where virus transmission is widespread should wear a mask, even if they are dealing with patients who are not believed to have the virus.

Tedros gave the example of a doctor doing rounds in a wing of a hospital with no known COVID-19 cases, saying that under the new guidelines, that doctor should be wearing a medical mask if there is known to be virus transmission in the wider community.

Additionally, after months of warning that medical masks should only be worn by health-care professionals and the most at-risk members of the public, in order to prevent a shortage, the WHO is now expanding that guidance.

"In areas with community transmission we advise that people aged 60 years or over or those with underlying conditions should wear a medical mask in situations where physical distancing is not possible," Tedros said.

Most of the other recommendations in the WHO's new guidelines are unchanged from the organization's last update to the document in April. Anyone caring for an infected person at home should wear a mask when in the same room as them and whenever they leave the house – something they should only do when "absolutely necessary."

Even when not in close contact with anyone who is sick, the WHO recommends that everyone "avoid crowded spaces and groups of people" according to the advice of local authorities and stay one metre away from everyone outside their household at all times.

"Current evidence suggests that most transmission of COVID-19 is occurring from symptomatic people to others in close contact, when not wearing appropriate [personal protective equipment]," the guidelines state.

Those advised to wear non-medical masks who are not able to obtain any may want to consider face shields as an alternative, the WHO said, although noting that a shield is "inferior to [a] mask with respect to prevention of droplet transmission."


Non-medical masks can be made from a wide variety of materials. During the pandemic, many have taken to making their own masks out of discarded clothes or other items they have at home.

According to the WHO, scientific evidence suggests that some materials are more effective than others at protecting droplets from spreading while still allowing their wearer to breathe with relative comfort. Knitted cotton – from a T-shirt, for example – and polypropylene produce some of the best results, while nylon and looser cotton such as that found in a handkerchief are less helpful.

The guidelines released Friday include the WHO's first specific recommendations for the ideal composition of a non-medical mask. They suggest a minimum of three layers, allowing for a filter between the material that touches the mouth and the material that is exposed to the outside world – and warn that additional layers could compromise breathability.

The agency suggests that the innermost layer be made of cotton or a similar material that bonds with water, while the outermost layer should be polyester, polypropylene or another material that repels water. Between the two, the WHO recommends a synthetic non-woven material or more cotton.

The WHO says masks should not be coated in wax or other substances because doing so will impair the wearer's ability to breathe. Non-medical masks should be changed whenever they are wet or visibly soiled, washed frequently, and thrown away once the fabrics "look noticeably worn out."