THE SCIENCE BEHIND THE MASK

How do face masks stop the virus spreading?

 

Face masks stop the virus spreading by trapping the water vapour that we breathe out. This water vapour is what carries the virus; while viruses themselves are small enough to pass through most materials, the small droplets of water vapour are not. Trap the water, trap (most of) the virus. 

We also breathe out smaller droplets, called aerosols. Because they are so small, they can stay in the air for few hours, and travel further than a few metres. There is emerging evidence that these aerosols from our breath can also carry the virus.

 

It's a good idea to wear a mask, because you don’t necessarily need to be right next to someone to share a breath!

Protecting others

 

The primary benefit of wearing a mask is that it protects others from ourselves. If we all successfully protect each other, then bam, we’ve defeated the virus.

It is far more effective to trap your breath as it is leaving your mouth and nose, rather than to prevent someone else’s breath from reaching your mouth and nose.

 

The droplets near your face are likely to be larger. As they move away into the air around you, they become aerosolized (the droplets becomes smaller and more spread out). It is important to try and trap the droplets while they are bigger and still close to your face, because that is when they are most likely to be caught by the fibres that make up your mask, instead of just passing through the gaps. 

Protecting you

 

While a non-medical face covering or mask will not provide a perfect seal and protect you from 100% of viral particles, it will still offer you some protection.

It is possible that the severity of illness that you are likely to suffer from will be partially dependent on how much of the virus you are exposed to (this is true for some other diseases), although the research at this stage suggests more complexity.

There is also a theorized “threshold” amount of virus that you need to be infected by, called the infectious dose, in order to fall ill. We don’t know what that is yet for covid-19.

If you wear a mask you will still be reducing the amount of aerosolized water vapour and viral particles that you breathe in. This means that you reduce the amount of virus that you are exposed to at any one time, hopefully reducing your chance of being exposed to an “infectious dose”, or a higher viral load.


Problems with wearing face masks
 

Struggling with your face mask? Check out Face Masks 101 here

 

 

Isn't there a higher risk of transmission? 

Wearing a face mask may increase the spread of the virus if it causes people to touch their face much more, without washing their hands, and then touch surfaces which become contaminated, or already are contaminated. 

You can reduce the risk of needing to touch your face, or adjust your face-mask, by picking out one that fits you well, and is comfortable to wear and breathe through. 

It is important that you wash or dispose of your face mask safely to avoid contaminating other surfaces, or catching the virus from the outside of the mask. You should always wash your hands before and after touching your face-mask. 

Face masks should not be used as an alternative to social distancing or good hand hygiene. You should still keep 2 metres away from people outside your household whenever possible, and wash your hands regularly. 

Will it affect my breathing? 

As long as they are made out of the right materials (e.g. cotton and breathable fabrics), face masks or coverings will not affect your breathing. There is no evidence to suggest that they will lower the oxygen concentration in your blood either. 

 

Doctors and medical staff wear face-masks for many hours at a time, all while performing complex medical procedures! 

How about people who cannot wear face masks?

Some people may struggle to wear a face-mask: people with sensory disorders such as autism; people with conditions such as asthma that already make breathing more difficult; and people with some mental illnesses, to name a few. Try not to challenge people who aren't wearing a face-mask unless you know them quite well - they may have valid reasons for choosing not to. 

They make communicating much more difficult

 

There are communication difficulties that come with wearing face masks; they make it harder to read and give facial expressions, which can be very important to people who are receiving care; they completely prevent lip-reading, which seriously impacts people with hearing difficulties who rely on lip-reading as a form of communication.

In some cases, a person may politely ask you to remove your mask in order to make communication easier. If this happens, try to stay 2 metres apart, and remove your face mask while communicating. If you don't feel comfortable doing this, then write things down.

There are types of face mask out there that have clear panels which means that people can see your lips through the face mask. These are less common than opaque face masks, because they are harder to construct, and it can be harder to get the right materials. They also have a tendency to fog up. 

If you would like to make communicator face masks, check out this pattern for the "Happy Turtle" face mask with a clear panel.

If you are already making communicator face masks and would like to share them, please add your details to:

UK Mask Network Database

Post in:

Buy, Sell, Donate, Accept Face Masks UK on Facebook 

or get involved with local community organisations, including Big Community Sew and Community Mask Trees

Bibliography

"If enough people use face masks, it could reduce the transmission rate to less than 1, which means the spread will reduce until the virus is wiped out!" 

and

It is far more effective to trap your breath as it is leaving your mouth and nose, rather than to prevent someone else’s breath from reaching your mouth and nose.

- Trisha Greenhalgh, paraphrased from interview at:


YouTube. 2020. RSM COVID-19 Series | Episode 6: Policymaking On Masks For General Public W/ Prof Trisha Greenhalgh. [online] Available at: <https://www.youtube.com/watch?v=3WuPLfTua2k> [Accessed 19 September 2020].


Her argument appears in more detail in this paper:

Greenhalgh, T., 2020. Face coverings for the public: Laying straw men to rest. Journal of Evaluation in Clinical Practice, 26(4), pp.1070-1077.


Referring to the model here (unpublished):

Tian, L. et. al, 2020. Calibrated Intervention And Containment Of The COVID-19 Pandemic. [ebook] unpublished. Available at: <https://covid-19.conacyt.mx/jspui/bitstream/1000/4645/1/1106972.pdf> [Accessed 19 September 2020].
 

Face masks stop the virus spreading by trapping the water vapour that we breathe out

and

Because they are so small, they can stay in the air for few hours, and travel further than a few metres.

Who.int. 2020. Transmission Of SARS-Cov-2: Implications For Infection Prevention Precautions. [online] Available at: <https://www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention-precautions> [Accessed 19 September 2020].

 

There is emerging evidence that these aerosols from our breath can also carry the virus.

Lednicky, J., Lauzardo, M., Fan, Z., Jutla, A., Tilly, T., Gangwar, M., Usmani, M., Shankar, S., Mohamed, K., Eiguren-Fernandez, A., Stephenson, C., Alam, M., Elbadry, M., Loeb, J., Subramaniam, K., Waltzek, T., Cherabuddi, K., Morris, J. and Wu, C., 2020. Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients.

(this is true for some other diseases), although the research at this stage suggests more complexity.

Heneghan, C., Brassey, J. and Jefferson, T., 2020. SARS-Cov-2 Viral Load And The Severity Of COVID-19 - CEBM. [online] CEBM. Available at: <https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/> [Accessed 19 September 2020].

There is also a theorized “threshold” amount of virus that you need to be infected by, called the infectious dose, in order to fall ill. 

Yezli, S. and Otter, J., 2011. Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment. Food and Environmental Virology, 3(1), pp.1-30.

If you wear a mask you will still be reducing the amount of aerosolized water vapour and viral particles that you breathe in. This means that you reduce the amount of virus that you are exposed to at any one time, hopefully reducing your chance of being exposed to an “infectious dose”, or a higher viral load.

Gandhi, M., Beyrer, C. and Goosby, E., 2020. Masks Do More Than Protect Others During COVID-19: Reducing the Inoculum of SARS-CoV-2 to Protect the Wearer. Journal of General Internal Medicine.

 
 
 
 
 
 
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