Julian Tang’s article on the airborne spread of Covid-19 and the need to prioritise control of aerosol spread of the virus (Understanding ‘aerosol transmission’ could be key to controlling coronavirus, 28 October) raises important issues about official guidance on social distancing, ie the 2 metre and 1 metre-plus rule.
This states: “Try to keep at least 2 metres away from people you do not live with … Where you cannot stay 2 metres apart you should stay more than 1 metre apart, as well as taking extra steps to stay safe. For example: wear a face covering … move outdoors … if indoors, make sure rooms are well ventilated by keeping windows and doors open.”
This advice clearly needs to be revised. While the risk is greatest near to an infected person, as Prof Tang says, virus-containing aerosols float through the air, and people further away could also become infected in poorly ventilated indoor spaces.
In my work as a GP with the NHS 111 Covid service, I have dealt with patients who have become infected indoors while observing 2 metre distancing, in the pub or at work behind Perspex screens, but not wearing masks. They were surprised to learn that the virus can spread through the air further than 2 metres. Social distancing is vital, but official guidance surely must now also say that we should improve ventilation and wear a mask at all times in indoor spaces with other people.
Dr Jonathan Fluxman
• Why does the government only emphasise washing, distance and masks, but never good ventilation? It has been obvious to me from the start that poorly ventilated interiors, such as in small shops, have atmospheres that are viral soups. The lack of emphasis on ventilation is insane.
It does have consequences. If my local chip shop has eight people standing 2 metres apart, what good is that if they are all breathing in virus-laden air? Or let’s say a father visits his daughter, goes through the house into the garden, and they stand 2 metres apart. If the daughter is infected, he will catch the virus while walking through the house; if he’s infected he’s spread the virus inside the house.
The government’s new motto should be “ventilation, ventilation, ventilation”. Open doors and windows, and try to achieve a through-draught. Don’t get into a cab if the windows are closed; don’t enter a shop if the front door is not open.
We need to urgently investigate how air-conditioning systems interact with the virus. That information will have enormous economic import in the near future.
• The Which? report (The face mask test: which are the best at limiting the spread of Covid?, 30 October) usefully draws our attention to the number of poor and excessively expensive masks now appearing on the market. It is a shame that the government, back in March, belittled the usefulness of masks in protecting against infection and transmission of the Covid virus.
The Which? filtration data is based on measurement of mechanical particle penetration and not on efficiency in use by humans, and takes no account of leakage during use. Better in vivo experiments have been carried out as long ago as 1975 (see my paper The Efficiency of Surgical Masks of Varying Design and Composition, British Journal of Surgery, vol 62), where it was shown that four-ply cotton muslin masks were 96.7% efficient in blocking bacterial infectious particles (after allowing for leakage), and actually improved on washing. This was a standard type of hospital mask at the time, and was better than four other mask types made from synthetic materials. In modern classification they would probably be rated FFP2.
There is now ample scientific evidence that this grade of mask not only protects patients against viruses in droplet infection but is as protective against respiratory viral infection as N95 (FFP3) respirators. A study published last year, N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel, found no difference between the protection afforded to wearers of either the mask or the (top grade) N95 respirator.
To state that surgical-grade masks do not protect the wearer is simply false. The importance of every person in every contact situation wearing a proper mask cannot be overemphasised. After total isolation, it is the most important means of preventing transmission of aerial infection.
Dr Louis B Quesnel
• Most years, around this time newspapers and magazines would soon be full of articles on how to cope with Christmas, about the pressure for perfection, the materialistic excess, the difficult in-laws, the drunken disputes and the ensuing debts. In the Covid environment, of course, everything seems different, so we find another way of longing for what we cannot have.
Talk of cancelling Christmas, that emotive phrase, must evoke a wry bitterness in those who have no family to see or who never meet up, for whatever reason, over the festive season. There is an irony in creating a hectic round of social engagements to mark the birth of one who came to bring peace to the world.
So perhaps we should use this year as an opportunity to simplify our celebrations, contact a friend or relative on their own and find a moment of quiet to contemplate the miracle of new life and the wonder of life itself. Even if it means the sacrifice of some happy moments, it will be worth it to save lives.
Rev Rachel Larkinson
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