The World Health Organisation (WHO) has released updated guidance on the use of medical and non-medical masks in communities and health care settings.
The organisation reviewed its position on masks in light of data from Hong Kong indicating that their widespread use in the community may have reduced the spread of coronavirus in some regions.
The updated WHO guidance, published on 6 April, does maintain that the use of masks could help reduce the spread of disease, but they are insufficient on their own. It is vital that hand hygiene and distancing is adhered to in conjunction with the use of any mask.
The report stresses that medical masks should be reserved for health care workers.
Professor David Heymann, of the London School of Hygiene and Tropical Medicine, who chaired the WHO’s scientific and technical advisory group for infectious hazards, said that unless people were working in healthcare settings, masks are “only for the protection of others, not for the protection of oneself”.
Guidance suggests that the use of masks in public settings can offer a false sense of security, potentially leading to less adherence to other preventive measures such as hand hygiene and distancing.
The report states: “There is no evidence that wearing a mask (whether medical or other types) by healthy persons in the wider community setting, including universal community masking, can prevent them from infection with respiratory viruses including COVID-19.”
This report appears to contradict recent advice from the US Centers for Disease Control and Prevention, which recommended the US public to wear cloth face coverings in pharmacies, groceries and other public places where physical distancing can be hard to maintain.
Though, according to the WHO, the use of masks made of other materials (e.g. cotton and other fabrics), also known as “non-medical” masks, has not been well evaluated.
Some research suggests that masks made of cotton may actually be a potential source of infection, as they are not resistant to fluids, meaning they could retain moisture and become contaminated. There is also the risk of self-contamination through mask touching and reuse (especially in relation to single use masks).
One study concerning the use of cloth masks in a healthcare facility found that health care workers using cotton cloth masks were at increased risk of infection compared with those who wore medical masks. Following this evidence the WHO states that cotton cloth masks are “not considered appropriate for health care workers.”
According to the updated advice from WHO, people with coronavirus symptoms should wear a face mask, self-isolate and seek medical advice as soon as they start to feel unwell, while those caring for them should wear a face mask when they are in the same room.
The WHO committee did acknowledge that the virus can be transmitted by people who are not exhibiting symptoms of COVID-19, but the virus must be spread via droplets or contaminated surfaces, which physical distancing and handwashing are intended to minimise.
Types of masks
Surgical masks and a N95 filtering facepiece respirators (FFRs) are different.
An N95 FFR is a type of respirator which removes particles from the air that are breathed through it. These respirators filter approximately 95% of very small (0.3 micron) particles. N95 FFRs are capable of filtering out all types of particles, including bacteria and viruses.
Surgical face masks are designed to act as a barrier against droplets including large respiratory particles (e.g. spit).
Both of these types of masks are reported as in scarce supply worldwide. They should be reserved for those who come in contact with the virus, such as health professionals.
Guidance on the WHO website remains that masks are effective only when used in combination with frequent hand-cleaning with alcohol-based hand rub or soap and water.
If you are healthy, a mask is only required for those taking care of a person with suspected symptoms or a confirmed COVID-19 diagnosis.