16 April 2020 UPDATE
This video released today by the BBC gives a useful synopsis on mask wearing.
7 April 2020 It seems that everyone is talking about either wearing or not wearing face masks. Some countries have made their use compulsory, others are telling their people there is no need to wear them. One world leader said in a briefing that wrapping a scarf around the face would give the same level of protection. Tutorials are springing up online with instructions on how to make your own, using anything from scraps of material to empty plastic bottles. Prices for masks are soaring as sellers realise they have a captive market for their product. Opinion is becoming increasingly divided so what are the facts about mask wearing? Without a doubt front line healthcare workers need medical grade masks as part of their PPE (Personal Protective Equipment). This is not negotiable. These medical grade masks are fitted to each individual. They are hot and uncomfortable to wear but absolutely essential for those on the front line. However, for the general public the argument for mask wearing is less clear cut. Any mask has to be used correctly and that includes how it is placed onto the face and how it is removed. The typical surgical mask serves to catch the droplets when a surgeon sneezes or cough in the operating theatre and to protect him/her from blood splatter whilst operating. It is made from paper and does not filter micro-organisms from the air. It was never designed to protect the wearer from air borne disease. Used incorrectly it is possible that the mask itself could become a source of infection. For example, imagine a COVID-19 positive person has coughed and sneezed into their mask. It has now become a reservoir of virus. They then take the mask off to eat and lay it on the table next to them. The table is now contaminated. They get into their car and place it on the dashboard, the dashboard is now contaminated. Masks should be carefully binned and a new one donned every 2 to 3 hours but many will keep it and continually re-use the same one. Masks may also give the wearer a false sense of security if they forego hand washing and social distancing in the mistaken belief that they are less vulnerable wearing a mask. To understand why masks do or don't work, and why front line staff need medical grade masks, we need to understand how viruses are spread. Viruses are spread by three main routes; direct touch, aerosol spread and the faecal-oral route. Direct touch results from the large respiratory droplets released in a sneeze or cough hitting a surface where they can then be physically picked up by another person. We know this is the main way COVID-19 spreads and this is why frequent hand washing and keeping our distance from each other is so necessary. In aerosol spread smaller droplets are breathed out, not sneezed or coughed out, and stay in the air for several hours and hence can be breathed in by other people. This is a risk for healthcare workers because of their close proximity to the patient and especially when they are carrying out procedures known as AGPs (aerosol generating procedures such as intubation - placing a tube into the airway). Aerosol spread does not seem to be the main mode of COVID-19 transmission for the general public. The faecal-oral route is most commonly seen in gastroenteritis infections but, whilst it may be a route of spread for COVID-19, it is not the prominent one. Studies over the years have compared the effectiveness of different masks. Medical grade masks block up to 95% of particles including many viruses, the basic surgical mask blocks around 40% but only the larger particles which excludes many viruses. Homemade fabric masks block anywhere between 1 and 20% of particles. All these studies have been small and vary in quality and reliability however it is clear that only medical grade masks can protect against aerosol transmission. There are no studies specifically on COVID-19 transmission and mask wearing but researchers at the University of East Anglia have today (6 April 2020) published their findings after studying all the available data on whether or not face masks help reduce the spread of illnesses similar in nature to COVID-19. Their conclusions were that the evidence is not strong enough to recommend widespread use of masks in the general population but they do have a role in supporting vulnerable people when they are in public places. Lead researcher Dr Julii Brainard said: “Overall, we found that the evidence was too uncertain to support the widespread use of face masks as a protective measure against COVID-19. However there is enough evidence to endorse the use of face masks for short periods of time by vulnerable individuals when in transient higher risk situations – such as on public transport or visiting shops. “Although we can support vulnerable people who choose to wear masks to avoid infection, we want to remind everyone that the people who most need to wear masks, to protect us all, are health care workers. We are all in more danger from COVID-19 if healthcare workers cannot obtain the safety equipment they need, which could happen if community demand for face masks becomes too high.” So, for the general public the message remains that the best way to protect yourself and others is to follow the government guidelines for social distancing and wash your hands regularly.
https://www.nature.com/articles/s41591-020-0843-2#Tab2 https://www.ncbi.nlm.nih.gov/pubmed/31668149 https://www.uea.ac.uk/about/-/face-masks-could-protect-vulnerable-people-against-coronavirus
