Why do we need to wear masks if the coronavirus is not airborne? At what temperature should I wash my cloth mask? Prof. Michael Borg, advisor to the European Centre for Disease Prevention and Control, past chair of the International Federation of Infection Control and consultant at Mater Dei, speaks to Sarah Carabott about masks and spread of COVID-19.

Viruses can be transmitted through droplets or aerosols. What is the difference?

Droplets are the spray you emit when sneezing. These small blobs of respiratory fluid fall to the ground within two metres. Aerosols originate from deep in the lungs, usually in infections like tuberculosis. Because they are smaller, they can be carried by air currents and can cause infections at distances further than two metres.

How is COVID-19 spread?

You primarily acquire COVID-19 by inhaling droplets from an infected person when closer than two metres or when touching your face after touching a surface where these droplets have deposited. Droplets originate from sneezing, coughing or loud talking, even if the person does not have symptoms. 

So COVID-19 is not spread through aerosols?

At this stage, it appears an unlikely method of spread. If it was, transmissibility would be greater. Without any intervention, one patient with coronavirus infects no more than 2.5 people, while a person with measles, which is dispersed by aerosols, infects at least 12. That is not to say that aerosol transmission can never happen. One outbreak involved choir singers who are trained to project their voice and therefore could potentially have formed some aerosols from the high velocity of air coming out of their lungs. Even then, it was impossible to exclude contact spread via hands.

The small number of clusters where aerosols have possibly been implicated have some things in common: large numbers of people without masks in enclosed, poorly ventilated, environments for a prolonged period, such as indoor restaurants and bars, gyms and singing sessions.

Why are we being asked to wear masks?

Masks provide a very effective barrier to stop your droplet spray. I cannot emphasise enough that you wear a mask to protect others. If we all wear masks, we will be protecting each other, including people who cannot wear them – such as very young children. Although not to the same degree, masks can also protect the user.

Wearing a mask is important but is not enough

Why cannot I touch my mask while wearing it?

Your mask should fit snugly on your face covering your mouth and nose. I see people continuously adjusting their mask. Every time you do so, you risk giving the coronavirus a piggyback on your hands… from a touched contaminated surface, such as a door handle, up to your face, especially your eyes. If it slips under the nose, or worse still, is worn under the chin like a fashion accessory, a mask becomes useless.

Why are masks preferred to visors?

A recent publication suggests that a good visor that bends around the side of the face and extends beyond the chin is as effective as a mask in protecting others. However, masks should be better at protecting users as they fit better around the face. Wearing a visor for a walk where you are far from people should be ok, but a mask is preferred in closed places where you cannot socially distance. If in doubt, just wear a mask.

Which type of mask should I wear?

The N-95 and FFP masks are only intended for specific hospital procedures where aerosols can sometimes be produced. Additionally, since they are intended for the self-protection of healthcare workers, many contain valves that make breathing out easier, meaning droplets will escape through the valve. Furthermore, European authorities have been alerted to the possibility of ‘dumping’ of poor-quality N-95 or FFP masks in Europe. Disposable surgical masks are extremely effective and are the main masks worn in hospitals. They are also good for the community but must be worn for no longer than six hours and should be thrown away after use. 

What about cloth masks?

Cloth masks can be a cost-effective alternative to disposable masks as they can be washed and reused, however, they need to be of good quality. Cloth masks should ideally be made of three layers with an inner cotton layer. The outer layers should be water repellant. Cloth masks should only be worn for two to three hours, placed in a plastic bag, and replaced with clean ones.

They must be washable up to at least five cycles at 60oC. Cloth masks are effective in protecting others, but their ability to protect the wearer remains under investigation.

Are masks the solution to the pandemic?

Masks will not perform miracles – we would otherwise not see COVID-19 increases in Europe where most countries have long mandated masks. Wearing a mask is important but is not enough. You also need to frequently wash or apply alcohol to your hands, avoid indoor venues and unnecessary crowds, including social and family gatherings.