UKC

Why 2m? WHO say 1m. I believe different countries have picked different distances too.

Is there any science at all behind the numbers or have they just picked at random?

Do they really mean don't touch each other or cough in someone's face, but don't think we can handle such a complex message?

And surely there is a difference with what is safe indoors and outdoors, so is 2m an indoor reference or an outdoor one?

Mainly thinking about this due to people on social media getting shouty about how reckless others are being on shared paths etc and so started pondering what the evidence was. 

Maybe it's like speeding, tell people the limit is 70 so they do 80, tell them to maintain 2 meters so they maintain 1.

And what about the wind speed factor?

The 2m separation was really intended for considerable contact; 15 minutes or so. It is based in studies of aerosol spread from still air coughs and sneezes.

For passing contact in the street, unless either party is coughing, sneezing, etc, the chance of receiving an infectious viral load is really quite low.

Now, that indoor separation is starting to be more relevant when returning to work in enclosed, air conditioned office spaces, as case studies I've seen in the US seem to suggest that enclosed, forced air spaces become infectious throughout... Quite how universal or accurate those findings are is another matter.

The sad thing is that we really don't seem to be getting the information we need on actual transmission mechanisms; how are the continuing cases getting exposed? What measures could we adopt to prevent similar infection?

And wind direction in relation to your moving direction!

These provisions are statistically driven - what can we ask people to do, that will be acceptable to enough people, that overall, nationwide, the Ro number will be low enough, that the infection rate will be manageable by the NHS.  It's not about what is the 'best' way to prevent infections spreading.

So 2m is better than one metre and allows for X% of dickheads to ignore it without compromising the overall effect. But if you are personally keen to lesson your chance of being infected, then 3m is somewhat better and 3 miles is ideal. Infact if you stay indoors with absolutely a minimal interaction with others, your chance of infection drops to practically zero - hence the advice for vulnerable to isolate themselves.

However it's obvious that the government's original plan to generate herd immunity is still their preferred option. So they're keen to make use of the spare capacity in intensive care to get as many people as possible infected, hence the piffle-waffle confusion, the mandating 2m social distancing but removal of the police's powers to enforce it, the unlimited travel, the shambolic return to work, etc, etc,

No, its just the distance which most large liquid droplets have dropped out of the air and is workable in most situations. If we use it as a rough guide we should be OK, it won't be perfect, the disease can even spread through airducts, but it is just one way to help keep the R value down. 

I suspected that people were getting upset unnecessarily about people passing them out and about.

I had heard about 15 mins being the key number, but haven't found where that actually comes from, do you know?

My guess on continuing cases getting exposed is that it is likely to be healthcare and other key workers bringing it home to families, possibly while being asymptomatic themselves so not distancing from family. Also, I have noticed lots of groups of teenagers hanging out in the woods (nice to see them rediscovering our pastimes!), who could asymptomatically spread it amongst themselves and then back to their families.

Just for accuracy. Nobody has removed the police powers to enforce it. The police have NEVER HAD the power to enforce it.

Interesting comment on the 2m rule earlier this week on Radio 4.

Droplets bigger than 5um fall out of the air within 1m, smaller droplets that can remain in the air and drift about have such small volume they're much less likely to contain enough virus to infect you. 

"More or Less, Vitamin D, explaining R and the 2 metre rule"

https://www.bbc.co.uk/sounds/play/m000j2r7 

This week's edition of 'More or Less' (Radio 4) has a good segment on the science behind this.

As Jim says, it's a statistical thing; it's not a hard and fast cutoff in time or distance.

Aerosol spread/fall depends on particulate size, and production method (e.g. bigger particles will go further with an initial sneeze, but will fall to ground quicker, whereas finer particles won't go as far initially, but will stay airborne longer, and may drift further). Then you need to consider the viral load in the spread of aerosol size...

I've seen some reasonable-looking study of such spread in one of the articles about the effectiveness of face coverings. I'll see if I can dig it out. But I think a search should yield results quite readily.

Hadn't heard that, but it tallies with my thinking...

Based on the size of droplets and how far they go I think.  https://mobile.twitter.com/delthiaricks/status/1244628956562755596

And the basic or home made masks might be good enough to catch the large droplets to reduce infections. Increasingly accepted worldwide rather than just in Asia, not sure what the evidence is.

Thanks for that, an interesting listen. 

The lady in front of me in the supermarket today had hers suitably loose to do nothing at all except make her feel safer. The many people I see with noses poking out over the top make me laugh too! If masks are to be advised, there should at least be a public information campaign (from actual health professionals) about how to wear, change and store them properly, and about not throwing them in hedgerows afterwards! 

There was a German study that used wind tunnels and they reckoned that outdoors you needed much more than 2m for runners and especially cyclists because their forward motion increased the distance behind them where there could still be droplets in the air.  So there was a cone of potential infection trailing off behind them rather than a 2m circle in all directions.   Although if they are healthy enough to be running or cycling their lungs probably aren't full of Covid.

With giving 30m of us a dose of a vaccine that's been rushed to production in 1/4 of the normal time by missing out most of the testing catching up fast on the inside.  Not much that could go wrong there.

Maybe. 

I think I had it in early Feb, the symptoms all add up. But, as it wasn't on our radar, I didn't stay at home. I went out running most days. The first km was truly hideous and then I felt amazing. I had expanded my lungs with enough force to allow me to hack up all the gunk that I couldn't at home and, presumably due to more oxygen getting into my system, the horrendous headache went away. I felt amazing for the rest of the run, came home and slept for ages. One day I decided not to run, to see if that helped me shift it quicker, and I felt so much worse. So I stuck to running every day after that!

Now, mine would obviously have been a mild case, if it was Covid, but interesting to see the effect running had. The cough was really horrible, it hurt so much to cough. I "slept" downstairs for ages because I coughed so much during the night that my husband couldn't sleep due to it! I've never had such a dramatic effect from running on any other illness.

A wind tunnel doesn't replicate real world conditions. How often are you running or cycling directly into the wind? Mostly the air is moving in different directions to you, so as your breath goes out from your mouth, the wind will blow it another way and disperse it further. My guess is (and the R4 link above seems to support this) that the viral load outside seems to be reduced a lot by virtue of dilution (dilution is the solution to pollution).

I will make sure to leave space next time I am in a wind tunnel though!

It was computer simulationed rather than windtunnels and was purely based on aerodynamics and the 'wake' one produces. I.e. how far away from you is the air you have breathed out into. There was no biomedical info in it, so no estimation of infection zones or whatever

It's like testing a plane in a wind tunnel, having wind blown at you is 'equivalent' to your own motion taking you forward through the air.

May be a different paper, I remember wind tunnel but I saw it on Twitter more than a week ago and I doubt I'd find it again easily.

I agree about the infection zones, I thought it was questionable too but the point about the shape of the cloud being different for someone who is moving  seemed valid.

Or you could be in a queue 2m behind an infected person. Each time the queue progresses you step into the air they've been breathing out etc. Big queue, slow, indoors etc.. but at least everyone feels good that 2m is stopping infections, when really it just slows transmission. 

A bit like the save lives mantra, really it's just delaying death, trying to make sure there will be a bed free for folk if they need it. 

Yes, so not real world conditions as it is not taking into account any turbulence caused by side winds and wind moving around trees, buildings etc or buffeting from cars and lorries. The real world air will not form the same wake that the wind tunnel will.

I hadn't thought about it in queues. I wonder what the airflow around shops is like with doors opening and closing etc. In the UK, I don't suppose many will have Aircon moving it around. But equally, you will breath more slowly and shallow breathing when standing in a slow moving queue, so maybe less is emitted?  

I haven't seen the study, but I think it is highly probable that the wake behind a cyclist, whether in a wind-tunnel or out-of-doors, is highly turbulent, which would tend to scatter any droplets all over the place by "mechanical dispersion".

But if it’s droplets, she won’t be breathing droplets out of her nose. They’ll be coming out of her mouth when she talks. The face covering are to stop the spread of droplets. 
 

If you step into someone’s air, the droplets are unlikely to have hung around. The heavy ones will have dropped, the light ones will evaporate very quickly. 
 

The R figure has dropped. It wouldn’t have dropped if it was being spread easily in supermarket queues. And remember that if you’re 2m behind someone then the next person is 4m away. So even if you catch it, the other people in the queue won’t. 

Slowing transmission until people recover before they infect somebody (R  < 1) is sufficient for the disease to be reduced to sporadic outbreaks.

If you believe the Cambridge results that happening already in London where R=0.4 and 24 infections per day predicted soon. 

South Korea has very good contact tracing. It would be interesting to know if the infections are in buildings and shared vehicles or if casually passing on the street without contact actually has any significant risk.

edit - not having a dig at you!

I don’t know for sure but I think wind tunnels and associated simulations and models are a bit more sophisticated, in 2020, than “a big fan blasting air in a single direction” 

So far , research ( first carried out in the 1940’s I think ) shows exponential decrease in infectious droplet and aerosol material at distances greater than 2 m.  
 As far as current knowledge goes , turbulent air flow outside further reduces risk by increasing dispersion.

Are you trying to say that you can't quite fathom it?

Damn. Good effort! In America that would have worked perfectly!

If it was the one I saw it was that the red, bigger droplets, did drop down.

But anyway I agree when running I think we should pull wider. I do most of my runs outside of town. I live in Worcester, MA, which is a small city, 200,000 people. I can drive 3-5 miles and run and see nobody. But in my state you can get a fine for running without a buff/face cover, I have one but have never used it because I largely just avoid people. If I see a runner I cross the road and run past them on the other side of the road.

The basic idea the further apart the safer you are is true. 2m is just whats workable in most situations, say in supermarkets, and we also know 2m is around the length of a person so its easy to estimate.

Because no one ever breathes heavily from their nose?

The issue being about how quickly is "quickly" - the "shoe-leather epidemiology" part of   https://www.erinbromage.com/post/the-risks-know-them-avoid-them   suggests that they may last for long enough to affect people at some range, if in an enclosed space; leading to the suggestion that masks may be helpful, at least indoors.

I think I saw the article about this study and it didn't appear to take that into consideration. Of course, the article could have been dumbed down. The picture used didn't seem to show any turbulence etc though

Isn't South Korea's current spike due to nightclubs reopening? (I can't for the life of me fathom why that seemed a good idea!)

Indeed, and I generally do. But I don't get upset if it can't happen. I have come across a lot of pairs of people walking together who then separate one to each side of the road or path, forcing me to go between them! This means I am closer to both of them than recommended, whereas if they had moved to the same side, I could have left the required distance, or at least close to it! I have been amazed at how often I come across this! A quiet back road that I use on my commute is one of the worst for it.

I had similar symptoms (relentless and enduring dry cough) in February following a visit to what is now acknowledged as a virus hotspot ski resort. BUT I experienced no fever or aches and pains, nor did my family contract the infection, apparently, so I put that down to coincidence. Did you have a fever or flu-type aches?

I didn't have a fever, I have never had one in my life. As for aches and pains, not really aches as such, but everything felt heavy and sluggish. 

Not everyone gets all symptoms, and particularly if you end up with a milder infection of it (not that the cough felt mild, but in relation to how badly some others get it I guess it was, if it was it!)

I had written it off as just some random other cough until I read about the happy hypoxia going on, and I thought about the effect that extra oxygen being forced into my lungs had. 

I will never know for sure if it was, by now I have definitely been exposed to it through work so if I have antibodies then we will never know if it was from that or from Feb. 

Hopefully you’re stuffed to the gills with antibodies!

I am presuming I must be by now! I guess we can never be sure, but if the PPE is as bad as people claim, then I have to have received a high enough viral load at work for my body to have created at least some antibodies. 

Not really. They tend to go downwards don’t they? The hairs in your nose hold a lot of  the droplets. And the droplets from your mouth tend to be from when you cough or speak. 
 

Indded. But we don’t know what the infectious dose is and with now less than 200 deaths a day the number of infections is well below 200k in the general population. With maybe 10-20k asymptomatic, so the likelihood of you meeting someone and walking through their quickly evaporating breath is now extremely small.  

I agree, it would seem like a sensible thing to tell the public to do (and educate them why) for enclosed spaces such as shops and public transport. Sadly, yet again we've gone for a half arsed "wear a mask if you feel like it" so the vast majority of people don't. So many other countries have made this mandatory while plucky old Britain does its own thing.....sounds familiar doesn't it?! 

Was it the Dutch/Belgian "study" that is going around social media? If so it was not a validated, peer reviewed scientific study https://www.bicycling.com/news/a32097735/coronavirus-viral-simulation/

This article is a an interesting analysis on how Coronavirus is spread in different environments:-

https://www.erinbromage.com/post/the-risks-know-them-avoid-them?fbclid=IwAR...

In lots of detail: https://www.bbc.co.uk/sounds/play/m000j2r7

If you don't want to listen to whole programme the bit on 2 metres starts at 13:30.

Masks are not advised. Face coverings are. 
 

There’s a big difference between wearing a face covering in an uncontrolled environment, and wearing a surgical mask in a hospital environment. 
 

I think a lot of people are missing this. 
 

You’d do your head in and disappear up your own orifice trying to maintain that level of infection control in the outside world. 

Yes, i have read this one and it sounds feasible, but also not peer reviewed yet so still to be taken with a pinch of salt. 

Easier to not bother and just keep away from people!! 

Yes, someone else linked to this higher up, it was indeed a good listen. 

I think ‘not bothering’ is a bit misleading. Wear a face covering. Put it in a bag when you take it off and wash your hands regularly are the key points. 
 

I ran into a wall when I went shopping and got back to the car. Keys were in my pocket. It just got silly from then on in. 

It was slightly tongue in cheek, but actually there are very few occasions where you can't just stay back, so most of the time you should just do that. Shops are limiting the people in them, so no need to be close there, just be patient. If it has self service tills then also no need to be close (I would put one on to protect a checkout worker). Outside - just leave space! 

That is very interesting. Essentially a disease of indoors or enclosed volumes (eg transport). In the call centre example infection determined by proximity of seating (for hours) rather than contamination of surfaces (toilets, door handles, lift buttons, photocopier etc) or briefly passing through lobby & sharing lift.

Turn off the air con & open the windows - doesn't really work for an open plan office twenty floors off the ground. 

If the point of a face covering for everyone is to stop other folk (asymptotic or otherwise) coughing and sneezing on the things you are about to pick up and put in your basket as well as helping to keep the staff who spend all day in the shop safe - I'm all for it!

Bit tricky, even on the ground floor of our offices: no opening windows anywhere, on any floor...

But my point was that poorly fitted coverings won't really acheive this. If you need to sneeze and have a face covering on (it is hayfever season, after all), your choice is to sneeze into the face covering and walk around with your manky sneezed in covering on your face, or remove it and use a hanky as normal. A poorly fitted mask won't even contain a lot of the sneeze as it will spray out all the gaps. Most will choose the latter. At work, I sneeze into the mask and then change the mask, but we have the luxury of a plentitude of masks and suitable clinical waste disposal bags to get rid of it. Without proper instruction on how to manage mask/ face covering wearing, they will not achieve their objective. Cover your mouth if you are going to sneeze or cough, stay back from people and you will be fine. Or, teach people properly how to use them.

I'm speaking from a position of relative ignorance here (doesn't stop anyone else, so hey-ho) but don't things moving through air tend to create concentated vortices behind them? 

That sounds unhealthy generally. 

I hate not being  able to open windows and get fresh air in.

Yeah, I too hate aircon.  Far rather opening windows.

200 deaths per day on a Sunday means about 500 on a Tuesday.

The 7 day average of 400 per day & down from a peak of 940 per day a month ago is a better indicator.

Yes and I agree with you in principle, my preference would be for people to be taught the benefits and to use them properly. The amount of time in a supermarket is not usually so long that you couldn't live with a snotty mask for a while and I'd much rather that than people half catching a sneeze (or not bothering at all) or taking out a snotty tissue and then touching things on shelves (which they then put back) or the check out machines etc. 

The vulnerable can't die twice. Infections could be up, but deaths down. 

The vulnerable have to catch it first. There’s many many more vulnerable people out there. 

Extrapolate back to 21 days ago when the people dying now were infected and adjust for people who are free of virus now and a few that it’s been passed on to. 

1.5m in South Korea, seem to have worked for them. Still erring on the side of caution, isn't really a problem for me.

Lots of posts across the net about 'Oh I had it in November or at christmas or in February'. Well Influenza A was peaking Nov/Dec and still elevated in Feb while Influenza B peaked in Feb. 

<200 per day is quoting the deceptive weekend glitch. 

Stick with 7 day rolling average if you want to communicate meaningful information.

I thought it was as meaningful as I could be. If you based it on 200 a day means that 21 days ago there were around 20,000 new infections, even at 400, that’s only 40,000. I have no idea what the R factor is now but we are told it’s less than 1. I’d be surprised if there are anything close to 20,000 cases at the moment. The 5/7/10 day rolling average if you want but without a true R figure it’s all guesses. 

My thoughts exactly, you'll get vortex shedding behind the moving cyclist, so rather than the droplets being widely dispersed as postulated, they'll form a plume of droplets held in the air in little concentrated vortices in the cyclists wake, just waiting to be inhaled.

Edit: Obviously wind speed and turbulence caused by solor radiation heating the ground (or not) will have an effect...

Given that a fever is also a key indicator of flu also, it really could be either. Flu seems to be more likely to give a runny nose and sneezing, which I didn't have. Early February is not unlikely for Covid, given that our first recorded case was late Feb. Plenty of customers at the wall will have been in ski resorts around that time so plenty of chance for me to come into contact with it. In fact, the Italian curling team were in the center around then too!

Either way, we will never know. I mostly found it interesting that running helped loads with whatever it is. 

Multi-million Pound question that. If 1m is deemed safe indoors it might be the difference between large swathes of the hospitality business going bust or not. 

See the link in Escher's post.

https://www.ukclimbing.com/forums/off_belay/the_2m_rule-719506?v=1#x9206000

Doesn't look good for hospitality.

It originates from bear attacks. No one who has successfully maintained 2m from a bear has ever died of a bear attack.

So, if I can run faster than the person I am with, am I safe from Covid then because it will attack them rather than me?! I can think of a good number of friends and family I can now socialise with!!

In pubs there’s proper contact between people. Consider what happens to your glass, how many hands it goes through, what happens when you refill it, where the bar staff hands go. 
 

We’d all have to be constantly washing our hands before each round and bar staff washing hands between pouring each round of drinks. 
 

I think in Sweden they have got round this by having table service. Clean glasses for each round bought to the table. 

I was thinking more restaurants than pubs - pubs are even harder to control. 

No. Don't be silly.

Because at 2m, if the other person falls over, they miss you. At 1m they would hit you 

In some cafes that are open there isn't any need to touch anything of a customers so constant washing isn't required.

Also so much of sweden is cash free already, card and phone app payments only. With a pinchos style system human interaction barely exists. 

Someone has to collect empty and dirty plates and glasses. If there are two staff then one can bring clean stuff out and another can be designated to just clear up, but I’m guessing that all gets a bit complex. 
 

I suspect the transmission is more likely to be between customers who are sitting together and handling things and putting them in their mouths, than someone bringing plates out and taking them away again.

I certainly will be avoiding any indoor eateries for the foreseeable future. I am planning to get a takeaway from one of the local restaurants for my birthday, but I can't see me going in anywhere to eat for a long time. Equally, I can imagine having friends over for a BBQ in the near-ish future, but probably not going into houses for a meal. Eating is definitely an aerosol generating procedure, and if done in enclosed spaces then the chance of viral load build up is increased a lot.  

Now that is interesting. I related in another chat that I and another woman caught it { I think it must have been Covid 19 but again unaware} at the same time in late february from a single third person with a terrible cough. Yes, the dreadful headache! But there were two of us,After recovery, I went on my long vigorous walks in sub zero, wind as hell Inverness and recovered faster than the younger woman who had a stationary lifestyle. Walking vigorously helped the chest- but I was not near anyone.

It's what you breathe (for an hour or two) not  what you  touch that seems the most important factor???

Transmitted between customers in restaurant to another table but not to serving staff.

Transmitted in office to those seated nearby but not others seated elsewhere who might use same lifts, toilets, photocopier, doors.

Transmitted within choir despite them trying to maintain distance and minimise touching.

I'd have thought the glass itself must be one of the biggest risk areas. lots of them sitting on shelves, a nice hard surface that could harbour a sneeze or a cough for quite a while. You have to put it in your mouth (it could be both contaminated or you could potentially contaminate it) and then someone has to take it away without touching any saliva on it and clean it properly. When I worked in bars we'd pick eight glasses up at once by sticking our hands into them and holding the bit your mouth touches - that'll have to change!   

There probably has to be a lot of virons for you to actually get sick with it. So a reasonable chance that someone sneezing would not project enough virons onto the glasses on a shelf (assuming they are not standing right next to them when they sneeze). As for clearing the glasses up, just wash hands each time you bring a load of glasses back to the kitchen. 

The build up of virus in the air from an the enclosed space is much bigger concern. Of we had the climate for outdoor dining, I wouldn't be too bothered about eating there. Indoors? Not for me!