Covid-19: should the public wear face masks?
BMJ 2020; 369 doi: https://doi.org/10.1136/bmj.m1442 (Published 09 April 2020) Cite this as: BMJ 2020;369:m1442Read our latest coverage of the coronavirus pandemic
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Dear Editor
There is controversy amongst the scientific community and western governments as to the strength of evidence to support face-mask use by the general public in slowing the spread of COVID-19, even if such use is limited to crowded spaces. It is often argued that face-masks may let the public drop their guard for social distancing, give a false sense of security, or even increase the risk of transmission if not put on or taken off properly. This is despite face-masks being extensively used in Asian countries which have been more successful in tackling the disease.
However, one may consider that lack of evidence does not necessarily equate to lack of benefit. It may just be challenging, if at all possible, for such evidence to be gathered.
There is no high quality evidence from randomised controlled trials that parachute use prevents death and harm when jumping off a plane[1,2], yet it might be considered unwise not to wear one if found in that situation. It is also unlikely that concerns about the parachute not being worn or deployed properly would discourage its use. Instead, appropriate training and guidance would be given to minimise improper use.
When dealing with a situation that can have devastating effects, in the absence of strong evidence, the principle of caution and common sense may allow the use of interventions that could have a positive impact with minimal potential harm.
1. Smith GC, Pell JP. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. BMJ. 2003 Dec 20;327(7429):1459-61.
2. Yeh RW, Valsdottir LR, Yeh MW, Shen C, Kramer DB, Strom JB, Secemsky EA, Healy JL, Domeier RM, Kazi DS, Nallamothu BK; PARACHUTE Investigators. Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial. BMJ. 2018 Dec 13;363:k5094. doi: 10.1136/bmj.k5094
Competing interests: No competing interests
Dear Editor
Covid-19 we should advise the public to wear face masks, BMJ 2020;369;m1435
I read with interest this excellent review of recent evidence for and against wearing masks in public.
Now as we are already several weeks into the lockdown and a mortality rate of over 30 000 and counting, we are still arguing about face masks.
We know for a fact that this virus is transmitted by way of droplets from carriers, symptomatic or asymptomatic, as they breath, talk or cough.
The risk of spread is higher in confined spaces with poor ventilation and where people cannot keep social distancing.
On the other hand, the risk of catching the virus in open spaces like walking in the streets or exercising in parks is negligible so no benefit in wearing face masks in these situations.
Unfortunately I am observing general disregard from hospital staff to social distancing due to one reason or another, possibly due to restricted or limited availability of space.
Coffee and staff rooms in theatres and on the wards as well as secretarial and managerial offices tend to be overcrowded.
Safe procedures among medical and nursing staff especially at handover is non-existent.
The need for some sort of face covering is crucial if we intend to limit the spread and reduce the incidence of infection. Not following this advice may be contributing to an unusually high infection rate among health workers.
A clear unambiguous policy on face covering is crucial if we intend to limit the spread in health care settings such as hospitals or care homes as well as private and public places where social distancing is not possible to maintain.
Competing interests: No competing interests
Dear Editor
The article titled “Face masks for the public during the covid-19 crisis” of 09 April 2020 (doi: https://doi.org/10.1136/bmj.m1435) and the editorial “Covid – 19: should the public wear face masks” written by Babak Javid et al (doi:10.1136/bmj.m1442) quite rightly do not pretend that there is any good evidence for the widespread wearing of face masks by the general public, but cite the precautionary principle as justification for supporting their use during the current covid-19 crisis.
Essentially the argument amounts to "it cannot do any harm". The precautionary principle relies upon any proposed action being without significant risk and it in this regard that the conclusion causes me concern. Professor Greenhalgh and colleagues do recognise concerns that masks may not be worn correctly, may engender a false sense of security and may give rise to a shortage of masks where they are most needed. However, these risks are all dismissed with little discussion.
I would argue that incorrect mask wearing in particular, is a serious concern which might result in an increased risk of spread: Incorrect fitting and removal, failure to undertake associated hand hygiene and touching / adjusting the mask during use do run a risk of contagion which could outweigh any benefits. Anecdotally, it is certainly true that many current mask wearers frequently touch and adjust them and release them to hang down around their necks. I accept that the evidence for any detrimental consequence from incorrect wearing of masks is poor, but evidence to support face mask wearing is also poor and for this reason the precautionary cannot be safely applied.
If face mask wearing by the public during the covid-19 crisis is to be supported it must, at least, be backed up by a strong public information campaign giving clear instructions on correct fitting, wearing and removal of face masks.
Competing interests: No competing interests
Dear Editor,
I would like to change the conversation on masks to visors for all. I have just dropped 34 off at an elder supported living facility and taken to wearing one for my weekly shop and yes someone sneezed near me. Apart from minor distortion in vision, not enough to prevent shopping, visors are instantly resusable, after washing in soap and water, the plastic is recyclable to prevent pollution, made in vast quantities by crafters, schools and firms up and down the UK and are cheap (£5 locally). But do they work? Yes, Yes!
'During testing of an influenza-laden cough aerosol with a volume median diameter (VMD) of 8.5 μm, wearing a face shield reduced the inhalational exposure of the worker by 96% in the period immediately after a cough' (Lindsley WG, Noti JD , Blachere FM , Szalajda JV, Beezhold DH. Efficacy of face shields against cough aerosol droplets from a cough simulator. J Occup Environ Hyg. 2014;11(8):509-518) and that was just one person with a visor, not the cough provider!
Visors stop us touching our faces and I know I touch my mask to tighten the metal over my nose as I speak, covers the H of eyes, nose and mouth, enables us to see expressions and lip read if needed, voice production is fairly clear, you could even sing in it, covers eyes and comfortable above glasses. Perencevich and colleagues in US have just published a similar view (Perencevich EN, Diekema DJ, Edmond MB. Moving Personal Protective Equipment Into the Community: Face Shields and Containment of COVID-19. JAMA. Published online April 29, 2020).
Finally, whilst I recommend for all visors are also easy to put on when elderly and vulnerable people go out and those who are mobility limited using wheelchairs, sticks and strollers, with their difficulty tying masks, visors maintain their position. We must continue with hygiene and physical distancing but let's see the conversation, not mask it.
Best wishes,
Jane Wilcock
Competing interests: No competing interests
Dear Editor,
Many of us have a visceral repulsion towards masks. We would literally rather die, or certainly risk serious harm, to ourselves and others, than live in a world where everyone wears a mask. It is a really frightening, horrible prospect, the beginning of the end for freedom, it takes away a great part of what makes life worth living, to see others and be seen by them. It will foster suspicion, depression and a mean spiritedness towards strangers, which already comes naturally to too many people.
How can you form new friendships if you can't see someone? How can you be yourself without facial expression? Maybe the authors don't have many friends anyway? Maybe they think preservation of life at all costs is justified? Maybe they don't think that question should be allowed to be asked?
I speak as someone who is not the slightest bit frightened by coronavirus - if it's your time, it's your time, have courage and face it. I wear a mask at work in the hospital but if I had to wear a mask all the time, I think I would become severely depressed, possibly suicidal, violent, or both, and I am a fairly nice, caring health professional!
Competing interests: No competing interests
Dear Editor,
I would like to congratulate and thank Prof Greenhalgh for the article titled “Face masks for the public during the covid-19 crisis” of 09 April 2020 (doi: https://doi.org/10.1136/bmj.m1435) and the editorial “Covid – 19: should the public wear face masks” written by Babak Javid et al (doi:10.1136/bmj.m1442)
It is highly commendable that the authors have raised this vital topical issue at such a high level that should draw the attention not only of the medical world but also of government officials, policy makers and the media.
The Covid 19 pandemic is already reaching biblical heights in terms of people affected and dead worldwide as well as its medium to long term potential effects on social, economic and health fronts. Everything must be done within our reach to minimise their magnitude and avoid any blunders committed on unreasonable grounds.
Many would argue that the first major blunder of delaying implementation of a total lockdown in the UK was committed on unjustifiable grounds, which has never been fully explained. The ambition of achieving herd immunity was unrealistic and frankly ludicrous. It was a well-known fact that approximately 70% of the UK’s population of 67 million would have to be infected by the virus to achieve herd immunity. It was also known from China experience that the overall mortality would be about 2%, which would have meant just under a million deaths in the UK. Therefore, it is still not clear to-date, why the scientific advisors and policy makers decided to delay the lockdown.
It would appear that the policy makers are already well on the way to committing the second blunder by actively discouraging the population from using facemasks. The reasons put forward to support this are non-credible and whimsical. The lack of evidence in favour of the facemask’s effectiveness in preventing the spread of viral infections has been translated into the evidence against it – as the authors have rightly pointed out. The fact that these negative results are based on poorly organised and poorly conducted studies has been ignored. The claims that the population will ignore the vital advice of physical distancing, respiratory and hand hygiene because of a false sense of security from facemasks is presumptive and biased. The claim that people would not wear masks correctly is a condescending attitude towards the masses. It seems illogical to ignore the facts that approximately 20% of infected people may be asymptomatic and that 40-80% of transmission can occur in the pre-symptomatic stage. In this context, it also seems illogical to ignore the fact that there is no evidence to suggest that using masks could be harmful in the given situation other than for the assumptions made by the UK policy makers as mentioned above.
Using a barrier to limit transmission of a disease that spreads by droplets or air borne methods is a no brainer, irrespective of how small the benefit might be. Even a small benefit at the grass roots is likely to be magnified manifold in a pandemic in which the numbers of infected persons and deaths are likely to be extremely high if spread of infection was not brought under control promptly. What is there to lose if all used facemasks? Yes, it would incur a cost but that would be minuscule in comparison to the cost of lives lost and its socioeconomic effects. Recommending the usage of innocuous facemasks that may very well have some benefits (at the least) is not the same as recommending use of treatments such as anti-malarial and anti-viral drugs that require careful evaluation of their effectiveness and side effects before they can be recommended for use.
Let us hope that good sense would prevail amongst the policy makers and widespread usage of facemask will be officially recommended without any further delay. The choice of the type of facemasks should be governed by their availability and all efforts should be made to increase their production and procurement. Not doing so will be yet another disastrous blunder that must be avoided at all costs.
Competing interests: No competing interests
Dear Editor
Javid et al acknowledge that “ In theory, wearing masks could instil a false sense of security”, but go on to say that, as concluded by Greenhalgh et al., “given the gravity of the pandemic, indirect evidence of benefit combined with the low risk of harm should outweigh the absence of direct evidence supporting mask wearing by the general public”.
There are significant problems with introducing a blanket policy for the public to wear face masks. Many of the limitations have already been pointed out by others including Javid et al, Greenhalgh et al and Martin et al (1-3). Not least, they are not infallible as isolators, masks vary in effectiveness for each situation thus rarely providing a total transmission barrier, the lack of availability of masks, they need to be fitted properly, there is a high risk of contamination and they need to be properly disposed of.
There is another most important, but not widely debated, danger relating to the potential risk of giving those who use them a false sense of security. This needs to be more carefully thought through because if wearing face masks impacts on people’s social distancing behaviour there could be serious repercussions.
We have direct human experimental evidence, which has been widely reviewed, that exhaled small and larger particles, even within short breaths, are transported in the exhaled air far beyond 1 metre (4). The underlying key elements of the transport processes involved are described in some detail in that paper with directions to more detailed mechanistic explanations published elsewhere. The clear conclusion is that a separation limit of 1 metre cannot be relied upon for personal safety purposes.
In a discussion in the same paper of the transport of respired aerosols associated with large volume breaths, the same underlying mechanistic processes were explained clearly with regard to how the exhaled airstream and its burden of incorporated particles can be expected to travel distances well in excess of 2 metres. Indeed the everyday experience of exhaling into a cold environment visibly demonstrates the considerable distance a coherent exhaled parcel of air can travel normally without necessarily spreading out into a diffuse dilute parcel of air and stopping its forward movement.
Our paper describes how an exhalation behaves and highlights how far it can travel. This direct experimental evidence of both small and large breath behaviour should be a warning to those who consider that exhaled air (and its particular content) is unlikely to travel a significant distance from its source.
Some, including Prof Robert Dingwall of Nottingham University and a member of NERVTAG whilst speaking on the BBC4,Today programme on 25th April, infer that the social distancing 2 metre ‘safety rule’ has effectively been plucked out of nowhere. Whilst there may be limited scientific evidence for use of the two metre rule in the present circumstances, there is clear scientific evidence based on direct experimentation in humans in real life situations, that one metre is not a sufficient distance to avoid transmission of particles between two humans. The use of a simple 2 metre distance rule may also be ineffective in many situations.
This known potential behaviour of exhaled air is vitally important when considering social distancing advice about people interacting with others – particularly those undertaking exertional exercise such as running which is associated with large volume exhalations and forces. In such circumstances a 2 metre separation is most unlikely to be an effective safety barrier, and its use should be urgently reviewed.
References
1 Javid B, Weekes M P, Matheson N J. Covid-19: should the public wear face masks? BMJ 2020; 369 :m1442
2. Greenhalgh T, Schmid M B, Czypionka T, Bassler D, Gruer L. Face masks for the public during the covid-19 crisis BMJ 2020; 369 :m1435
3 Martin GP, Hanna E, Dingwall R. Rapid Response to Greenhalgh et al.: Face masks, the precautionary principle, and evidence-informed policy. 22nd April 2020.
https://www.bmj.com/content/369/bmj.m1435/rr-43
4. Denison D, Porter A, Mills M, Schroter RC. Forensic implications of respiratory derived blood spatter distributions. Forensic Sci Int. 2011 Jan 30;204(1-3):144-55. doi: 10.1016/j.forsciint.2010.05.017. Epub 2010 Jun 18
Competing interests: No competing interests
Dear Editor,
Many of the arguments against the wearing of face masks in public are easily countered.
For example: reusable cloth masks may be made from readily available antimicrobial materials preventing them from becoming a reservoir for the virus; they may easily be decontaminated by a 60C wash, or even a few minutes in a tumble dryer at 80C; and the risks from face-touching may be reduced by the use of antimicrobial products on the skin and lips e.g. sunscreen, lipstick, eye liner and face creams containing TiO2.
If the argument before such considerations is equipoised then after it would be expected to favour wearing.
Competing interests: No competing interests
Dear Editor
Firstly I would like to thank Prof Greenhalgh for her superb leadership and seemingly limitless energy. Perhaps she can share her secrets to this in another editorial? And if not already, I would highly recommend your readers to add themselves to Prof's 68.7K followers on Twitter @trishgreenhalgh for a cutting edge source of profound wisdom and knowledge.
Like many, I have been sleeping less (aka Covsomia ?) due to increased work pressures during the day, and much of my evening and spare time becoming consumed by emails (often with large attachments), up-updated guidelines, news reports and social media. The growing body of research into the use of face covering, and the varying approaches internationally has been fascinating to follow. It seems now that there is indeed good evidence to support the widespread use of face covering - especially knowing that they greatly reduce transmission, and "that 40-80% of transmission events occur from people who are presymptomatic or asymptomatic" .
I like to trust expert evidence advice, but have 3 observations to make:
1) until the Coronavirus Pandemic has settled, should all health care (& key workers) now be asking all patients (or clients) they are seeing to wear a face covering at all times? At Bridgewater Surgeries, we started this practice based on our own clinical judgement from 23.3.2020, and it certainly made us feel more protected.
2) Ash Paul, Public Health Specialist posted this Tweet on 17.4.2020 https://twitter.com/pash22/status/1251260489067266050?s=20
with the link https://m.box.com/shared_item/https%3A%2F%2Fstanfordmedicine.app.box.com...
This scientific information suggests that any face covering is highly effective (and in fact Vacuum cleaner bags are second best to a mask). Thank you Ash Paul for all your fantastic resources @pash22
3) should we / the press now think about using the term FACE COVERING rather than 'mask' in a non health care setting , to help prevent the general public seeking out PPE that could further exacerbate known PPE shortages ?
I attach a link to a Tweet from Prof Greenhalgh herself agreeing with the term FACE COVERING.:
https://twitter.com/trishgreenhalgh/status/1253228281387724801?s=20
Do please note this Tweet is dated 23.4.2020, and the BMJ Editorial was published on 9.4.2020.
Hoping that you all keep safe & well, and looking forward - as we all are - to a return to 'normal'
Yours sincerely
Simon
Competing interests: I own a Dyson - see point 2 in my response for the explanation
Covid-19: face masks, airplane travel, international tourism, politics and economics
Dear Editor
As person-to-person transmission is becoming increasingly recognised as a potentially serious contributor to person-person transmission of covid-19, (1) the debate over the wearing of face masks in public places is becoming ever more energetic.
Equally, people are now displaying increasing interest in travelling overseas for the purposes of vacationing. (2)
Pertinent to this is a recent article by Daon et al in the Journal of Travel Medicine, regarding the high potential for airborne spread of covid-19 on air flights. (3)
It is thus clear that airplane travel can pose a risk of covid-19 dissemination, not only in terms of transporting covid-19 from one country to another but also between individuals during the flight itself.
Beyond that, while there are clearly issues around air flights and covid-19 that need worked out and remedied, it is becoming increasingly evident that there are vast economic concerns around travel and tourism, for governments, for the destinations that air travelers visit, and for the airlines themselves.
For example, as with parts of the wider tourism industry, the future of at least some airlines is currently uncertain. (4) For example the business model for running a viable budget airline involves filling airplanes with high numbers of travelers, (5) with currently little scope for prioritising social distancing. Equally, while the public debate around mandatory face mask wearing in general is growing in volume, (6) the argument as to whether or not face masks provide adequate protection against covid-19 during flights, and how vigorously the wearing of them should be enforced, also remains energetic. (7)
Governments and politicians are inevitably involved, and indeed they simply have to be. Some may be governing in places where incoming tourism is a staple industry. Some have to deal with the fact that up till now a great many of their populations have enjoyed travelling on airplanes to pleasurable and exciting destinations and in all likelihood would, post-pandemic, want to be able to pick up exactly where they left off. Some countries run major airlines. All governments and politicians are faced with covid-19 concerns.
Accordingly, there are a number of issues that merit attention.
Firstly, the magnitude of the risks associated with air flights and their potential to facilitate the spread of covid-19, not just between individuals but also across long distances and between countries, needs to be fully established, and policies to deal with that developed agreed upon by all relevant players.
Secondly, it is clear that there are two important issues presented here that have the potential to come into conflict. Firstly, for many countries the economic importance of the high levels of spending by the public on international tourism and air travel cannot be ignored. Secondly, covid-19 is a transmissible and potentially lethal infectious disease, and accordingly public health concerns are legitimate and have to be taken very seriously and prioritised, including during air travel.
As long as covid-19 remains a clear and present danger to human beings, politicians, governments, regulators and international authorities will have to work closely with airlines and the tourism industry in general - and think laterally and imaginatively if an acceptable way forward out of this maelstrom of health-related, political and economic considerations is to be found.
References
1. Zhang R, Li Y, Zhang AL, Wang Y, and Molina MJ. Identifying airborne transmission as the dominant route for the spread of COVID-19. PNAS 2020: 117; 14857-14863. https://doi.org/10.1073/pnas.2009637117
2. Anonymous. Coronavirus: Where can I go on holiday? A guide to destinations. BBC News, 21 July 2020. https://www.bbc.co.uk/news/uk-53249747.
3. Daon Y, Thompson RN, Obolski U. Estimating COVID-19 outbreak risk through air travel. J Travel Med, 2020, June 5; taaa093. https://doi.org/10.1093/jtm/taaa093.
4. Anonymous. Budget airlines face business model challenge in post-pandemic world. Kyodo News, June 9, 2020. https://english.kyodonews.net/news/2020/06/f4119587beab-budget-airlines-....
5. Grabianowski E. How Budget Airlines Work. HowStuffWorks, March 12, 2009. https://money.howstuffworks.com/personal-finance/budgeting/budget-airlin....
6. Blackburn P. Government makes wearing face masks mandatory. BMA, July 14, 2020. https://www.bma.org.uk/news-and-opinion/government-makes-wearing-face-ma...
7. Mzezewa T. Airlines say everybody onboard must wear a mask. So why aren’t they?. New York Times, July 8, 2020. https://www.nytimes.com/2020/06/04/travel/coronavirus-flying-face-masks....
Competing interests: No competing interests