That is some 10 per day per hundred thousand. Taking that day as an example, this analysis suggests that would mean some 250 infectious people would be on the streets of Swindon, out and about shopping, having a pint, getting their hair cut and everything else we can now do. Those infectious people could be working in a shop, office or factory.
The problem is we just don't know who. Neither do they. There are no obvious signs.
You'll also know that there are some 250 people you could bump into who are infectious with COVID-19.
But you don't know who.
Putting this information together, you would naturally treat everybody you meet with suspicion. You would be much happier if they were wearing a mask. They would be looking at you and thinking the same thing. If you weren't wearing a mask, they would regard you as a risk. Quite possibly an unacceptable risk to be shunned. But why the risk? And how does a mask help?
HOW A MASK WORKS
We keep being told to wash our hands, and so we should. But it is now recognised that the most common form of transmission of the virus from one person to another is viruses in the microdroplets of water commonly known as "aerosols". These are "less than 5 microns, or about one tenth the width of a human hair". When we talk, shout, laugh or sing we give off a cloud of microdroplets. In the winter we see them condense as we breathe out.
Indeed, "just two to three minutes of talking can produce as many droplets as one cough".
Aerosols can hang around in still air, with the viruses remaining viable and infectious for four hours or more, having a half life of around 1.2 hours. If we are outside, the slightest breeze can take them away. But in a lift or un-ventilated space, we can easily breathe somebody else's aerosols in, such as if they are sitting nearby. Indoors in a well-ventilated area is better, though the airflow can spread it to other people over a greater distance.
Larger droplets that are visible, when someone spits them out when talking, singing or coughing, tend to fall to the ground fairly quickly. So they are less of a problem outside of healthcare settings.
Fortunately even a single layer of fabric can stop these aerosols to a certain extent, and of course will stop larger droplets. Masks that are triple layer, like commercially available "surgical" or "medical" masks, are more effective. As are fabric masks with a pocket for a paper tissue. Not perfect, but very good.
If we can stop an infectious person giving out viruses in aerosols, then they won't be breathed in by other people. Transmission of infection avoided. That's what a mask or face covering does.
The principle being "My mask protects you. Yours protects me." Although wearing a mask does also provide a little protection to the wearer.
Here's Dr Fauci, the top infectious disease expert in America talking about these topics relevant to this blogpost:
- The importance of aerosols compared to surfaces
- His support for the use of face masks
- LongCOVID "symptoms even when the virus has gone"
A mask also cuts down you touching your mouth or nose, either to pick up viruses to infect others or infect yourself with viruses. So a bonus there too
But when you can, it is still best to observe social distancing and keep one or two metres apart from other people. When wearing a mask it is more likely the wearer will ignore social distancing, which is why Sweden does not yet recommend them. But here in the UK, social distancing is difficult, and wearing masks is well worthwhile.
Here's the results of a mathematical model of the risks of aerosol-based transmission indoors. Clearly the more people are talking, and the longer you are with them, the more likely that you would become infected if someone nearby is infectious.
WHAT IF I'VE ALREADY HAD COVID-19?
The level of asymptomatic carriers of the virus suggests you can catch it again, be infectious, but remain asymptomatic. Until that is disproved, we have to assume that having had COVID-19 means you could still be infectious with a subsequent dose.
WHAT DOES IT MEAN NOT TO BE WEARING A MASK?
Given that anybody can be infectious without realising it, not to wear a mask means:
- You don't understand the principle of "My mask protects you. Yours protects me." and how a mask or face covering works, and/or
- You're utterly selfish
Here are some common myths being used to try to avoid wearing a mask.
There are a few people who have a genuine medical reason not to wear a mask, but they are being advised to wear one whenever possible. The British Heart Foundation provides a lot of advice here, including: "Most people who have a health condition won’t experience any problems with wearing a face mask, especially once they get used to wearing one. If you do struggle with your breathing and find that wearing a face mask makes it worse, you do not have to wear one. In all of the UK nations, you are exempt from wearing a face covering if it causes you severe distress. If you are experiencing anxiety about wearing a face mask, Mind has practical tips on how to cope."
Personally I have found two types of Surgical Masks perfectly breathable, unless exertion means I'm having to breathe more heavily. Then a mask with elastic ear straps makes it easier to move the mask temporarily out of the way, carefully under my chin without touching the mask fabric. Then cover my mouth and nose again when I can.
IS IT WORTH WEARING A MASK OUTDOORS?
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| With elasticated ear straps |
The other type has fixed straps which mean the mask can't be pulled down. In both cases I find the easiest thing to do is put my mask on as I leave the house.
Outdoors is safer than indoors, but is not risk free. So to be sure I tend to ensure I cover my mouth and nose whenever I pass someone in the street.
ARE THERE MASKS AVAILABLE THAT PROTECT ME?
Yes, I'm altruistic, unselfish and happy to wear a mask to protect others in case I am infectious. Especially as others are doing so to protect me. But are there masks available that I can wear that also protect me?
An important question that another separate blogpost addresses, including cheap home-made face coverings.
INFECTION RATES
If there are 250 infectious people out and about in Swindon, that's obviously a concern. What about if that was reduced to 25? Would that still be a concern for you? Or would you be happier if there were only 2 or 3? I would.
That means getting new cases down to #NearZero , less than a real 2 new infections a day per hundred thousand.
That's under 1000 new a day across the 55 million population of England, as Professor Chris Whitty suggested back in May. Equivalent to 200 official "Confirmed New Cases", given the true number is around five times the official.
IN CONCLUSION
We know there are six nasty risks of COVID-19 including death and LongCOVID. So we need to take this disease seriously.
Masks are an effective way of reducing the spread of infection. "My mask protects you. Yours protects me". That works best when everybody does it.
An assesment of the different masks types, and what works best is here.
In addition, we need to get daily infections down to #NearZero. Masks will play an important role in achieving that, and then in keeping the rate very low.
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