Woman wearing surgical face mask

University of Hull virologist answers biggest questions on COVID-19 face masks

Wearing a face covering in shops and supermarkets in England is to become mandatory from 24 July, under new Government guidance in response to COVID-19.

Those who fail to comply with the new rules will face a fine of up to £100. Health Secretary Matt Hancock said it would "give people more confidence to shop safely and enhance protections for those who work in shops.”

Dr Cheryl Walter is a virologist at the University of Hull, with more than 15 years of experience working on a variety of viruses and virus-host systems.

Here, Dr Walter answers some of the biggest questions – submitted by Hull Daily Mail – on the use of face masks amid the COVID-19 pandemic.

Dr Cheryl Walter

How do masks help prevent the spread of Coronavirus?

Coronavirus (SARS-CoV-2) causes a respiratory infection that has been termed COVID-19. Like most respiratory infections, it can be spread from person to person in droplets and/or aerosols. Masks help to catch the droplets that we breath out and breath in.

Is there any point in wearing a mask if so few others around you are not?

Definitely! Although the people around you might not have COVID-19, you might be infected and not yet be aware of it. So, by wearing a mask, you protect those around you that aren’t wearing a mask from infection.

If you are not infected or immune to COVID-19, masks are highly likely to reduce the rate of transmission of COVID-19 disease, meaning they do work, to varying extents. Masks have got to be worn correctly and there will be differences in the varying grades of masks that are available.

Why is the Government advice now changing on the use of face masks?  

I think it’s a mixture of things that have led to the decision. Part-political and partly based on emerging evidence about the usefulness of wearing a facemask in preventing the spread of COVID-19.

There have been fears wearing a mask may provide a false sense of security. Do you feel this is the case?  

I hope not. I think it might for some people who feel it is a substitute for social distancing. On the other hand, I think most people who are conscious enough to wear a mask, are also aware of the other guidelines in this health crisis.

Where should masks be worn? Should you wear one outside?  

They should be worn indoors, outside of your own home, around someone who is ill with COVID-19 and in crowded areas outside.

Are there any differences between wearing a face covering and a face mask and, if so, what are they?

A face covering made out of fabric will stop a large proportion of large droplets from being breathed beyond the mask or in, if you are in close proximity to someone who is infectious.

Medical grade masks come in a few grades and the higher the grade, the smaller the droplets they can filter out. Scientists are still not sure how small the droplets are that still contain virus. The smaller the droplet, the more difficult it is to sieve them out with a mask and the longer they stay in the air.

Who is exempt from wearing masks and why?

  • Young children under the age of 11
  • Not being able to put on, wear or remove a face covering because of a physical or mental illness or impairment, or disability
  • If putting on, wearing or removing a face covering will cause you severe distress
  • If you are travelling with, or helping, someone who relies on lip reading to communicate
  • To avoid harm or injury, or the risk of harm or injury, to yourself or others
  • To avoid injury, or to escape a risk of harm, and you do not have a face covering with you

Can disposable masks be worn more than once and how long can they be worn before they become ineffective?  

Have a look at the guidance on the mask – they usually have a certain number of hours wear in them.

The risk comes when you put the mask on and off repeatedly. This is when you could touch a contaminated patch on the outside of the mask and accidentally infect yourself. 

Although they are not good for the environment, it is probably safer to discard disposable masks after each use. Don’t forget to wash your hands once you have done so. 

How do you feel about masks personally? Do you wear one and, if so, wear and when? 

I think they are literally lifesavers. They are not 100% effective but they do help a lot, along with social distancing and handwashing, in preventing transmission of COVID-19. I wear one whenever I go out the shops.

Media Enquiries

Please contact the Press Office on