SARS-CoV-2 Infectivity

[Pucksoppet]

I tuned into a Radio 4 programme yesterday part way through, so I don't know which it was, where they were describing experiments done with face-masks and flu & common cold coronaviruses.

I learned several things from it:

1) Being momentarily closer than 2 metres to someone infected doesn't mean you will inevitably be infected yourself. The finding was you needed to have at least 15 minutes close contact (e.g. face-to-face conversation) before the risk of infection became significant.

2) They sampled the air in a room with infected people in it, both wearing and not wearing masks, and the outcome was that yes, indeed masks reduce the viral load in the air, but that in most cases the viral load in the air anyway was small. Only a small number of people released large amounts of virus.

If anyone can tell me the programme and give a link to the work, I would be grateful.

It's relevant, because physical distancing rules vary between countries: some are 2 metres, some are 1 metre. It looks like the USA is on the cusp of recommending people to wear masks (which I'm really not sure is a good idea, as it will likely cause huge demand, which could reduce the amount available for healthcare workers in other countries). Similarly, reports are the WHO may recommend people wear mask.

I could easily have got the wrong end of the stick, so I welcome corrections, and this could be a really good illustration of Chinese whispers, or me "...hearing what I want to hear and disregarding the rest.".

[AMS]

What time was it on?

I'd be interested to listen, as I've been wondering where the 2 metres thing comes from. (This was after seeing the 2 m spacing marked out for both the queue outside our local tesco express and inside the store itself.)

It does also point to public transport being the most risky setting, which is presumably why it's taken hold faster in London than elsewhere in the UK.

[shpalman]

https://www.bostonglobe.com/2020/03/31/ ... ssor-says/

MIT sneeze stuff.

[Pucksoppet]

https://www.bostonglobe.com/2020/03/31/ ... ssor-says/

MIT sneeze stuff.

Thanks for that: for me it is behind a paywall, but a bit of CSS hacking allowed me to find the source publication:


Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19
Lydia Bourouiba, PhD1
Author Affiliations Article Information
JAMA. Published online March 26, 2020. doi:10.1001/jama.2020.4756

[Pucksoppet]

What time was it on?

I'd be interested to listen, as I've been wondering where the 2 metres thing comes from. (This was after seeing the 2 m spacing marked out for both the queue outside our local tesco express and inside the store itself.)

It does also point to public transport being the most risky setting, which is presumably why it's taken hold faster in London than elsewhere in the UK.

Found it. It was World at One. Available on the BBC Sounds website for the next 28 days.

https://www.bbc.co.uk/sounds/play/m000gvms

Section on masks starts at 22min54secs. Refers to a Nature Medicine Brief Communication. Finishes at 26m50s.

Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med (2020). https://doi.org/10.1038/s41591-020-0843-2

Or 'Shareable link': https://rdcu.be/b3odT

We identified seasonal human coronaviruses, influenza viruses and rhinoviruses in exhaled breath and coughs of children and adults with acute respiratory illness. Surgical face masks significantly reduced detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets. Our results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals.

Interviewed Dr. Ben Cowling of the University of Hong Kong, who made some quite interesting comments, including saying (possibly some) people infected with SARA-CoV-2 were not very contagious. I wish there was a transcript.

[Stranger Mouse]

I posted this on another thread but this podcast on airborne and aerosol transmission is brilliant

https://gimletmedia.com/shows/science-vs/v4heg36

[Pucksoppet]

I posted this on another thread but this podcast on airborne and aerosol transmission is brilliant

https://gimletmedia.com/shows/science-vs/v4heg36

Thank you for that. They kindly provide a transcript.

Short form url: https://bit.ly/3aI1kAE

End up here: https://docs.google.com/document/d/e/2P ... Sk9Rk8/pub

[Boustrophedon]

It would appear, contrary to all those posts on Facebook, that cats can get it and presumably pass it on.

https://edition.cnn.com/2020/04/05/us/t ... zf0rnzveTs

[Gfamily]

It would appear, contrary to all those posts on Facebook, that cats can get it and presumably pass it on.

https://edition.cnn.com/2020/04/05/us/t ... zf0rnzveTs

Cats and ferrets are known to be susceptible to Coronaviruses in general.
I don't know if there's any known transmission from cat to human.

[Stranger Mouse]

I posted this on another thread but this podcast on airborne and aerosol transmission is brilliant

https://gimletmedia.com/shows/science-vs/v4heg36

Thank you for that. They kindly provide a transcript.

Short form url: https://bit.ly/3aI1kAE

End up here: https://docs.google.com/document/d/e/2P ... Sk9Rk8/pub

The second part on disinfecting things is out now. This is fast becoming my favourite science podcast

Podcast https://gimletmedia.com/shows/science-vs/emhwnb5


Transcript https://docs.google.com/document/d/e/2P ... rEukyA/pub

[Pucksoppet]

I posted this on another thread but this podcast on airborne and aerosol transmission is brilliant

https://gimletmedia.com/shows/science-vs/v4heg36

Thank you for that. They kindly provide a transcript.

Short form url: https://bit.ly/3aI1kAE

End up here: https://docs.google.com/document/d/e/2P ... Sk9Rk8/pub

The second part on disinfecting things is out now. This is fast becoming my favourite science podcast

Podcast https://gimletmedia.com/shows/science-vs/emhwnb5


Transcript https://docs.google.com/document/d/e/2P ... rEukyA/pub

I love the extensive list of references in the footnotes on the transcript. And I love the fact there is a transcript. Really, really good.

[raven]

I posted this on another thread but this podcast on airborne and aerosol transmission is brilliant

https://gimletmedia.com/shows/science-vs/v4heg36

I am very much liking that too, and that there's a transcript.

Also loving that maybe I wasn't so crazy to wipe down a bag of cornflakes earlier this week... There was only one box left of the brand we both like, but some eejit had torn the top open. So I bought it, took out the bag inside that had been exposed to the evulz of supermarket air, and washed it a bit. With soapy warm water.

Other than that, I've only changed my shopping habit by apopting a 'touch it, must buy it' rule, so I don't feel guilty about leaving traces all over the place for someone else.

Speaking of which, I saw a woman in the supermarket last week who had gloves on. She also had a pen and a list, and she kept putting the pen between her teeth to free up her hands. I kinda felt I should point out how silly that was, but it was too late, she'd already done it, and I didn't want to stress her out.

Now I realise she wasn't just providing a route from envirionment to her mouth, she was also potentially smearing her spit everywhere and perhaps I should have said something.

[AMS]

Speaking of which, I saw a woman in the supermarket last week who had gloves on. She also had a pen and a list, and she kept putting the pen between her teeth to free up her hands. I kinda felt I should point out how silly that was, but it was too late, she'd already done it, and I didn't want to stress her out.

Now I realise she wasn't just providing a route from envirionment to her mouth, she was also potentially smearing her spit everywhere and perhaps I should have said something.

This reminded me of the set-up at our local tesco express. They have a bottle of cleaning spray and a roll of disposable cloths for wiping the basket handles. Which is great, except it means the one thing everyone touches is the spray bottle's trigger.

[Gfamily]

Speaking of which, I saw a woman in the supermarket last week who had gloves on. She also had a pen and a list, and she kept putting the pen between her teeth to free up her hands. I kinda felt I should point out how silly that was, but it was too late, she'd already done it, and I didn't want to stress her out.

Now I realise she wasn't just providing a route from envirionment to her mouth, she was also potentially smearing her spit everywhere and perhaps I should have said something.

This reminded me of the set-up at our local tesco express. They have a bottle of cleaning spray and a roll of disposable cloths for wiping the basket handles. Which is great, except it means the one thing everyone touches is the spray bottle's trigger.

Tricky isn't it. But let's not make perfection the enemy of the good.

[science_fox]

Speaking of which, I saw a woman in the supermarket last week who had gloves on. She also had a pen and a list, and she kept putting the pen between her teeth to free up her hands. I kinda felt I should point out how silly that was, but it was too late, she'd already done it, and I didn't want to stress her out.

Now I realise she wasn't just providing a route from envirionment to her mouth, she was also potentially smearing her spit everywhere and perhaps I should have said something.

This reminded me of the set-up at our local tesco express. They have a bottle of cleaning spray and a roll of disposable cloths for wiping the basket handles. Which is great, except it means the one thing everyone touches is the spray bottle's trigger.

Tricky isn't it. But let's not make perfection the enemy of the good.

Viral load is important*. So from a very small surface area you're unlikely to pick up as much as a larger area.

*Well normally. They don't actually know specifically for this one, it doesn't seem to correlate that well with severity that much possibly because of the cytokine storm effects, but may do with transmission which is hard to monitor without enough testing.. Why is life so complicated

[Bird on a Fire]

You'll also touch the spray bottle very briefly, whereas the trolley will spend a long time being handled, and sitting under your face while you breathe and speak and stuff.

[raven]

At least Tescos is giving you the option, though. Sainsbury's don't have anything to wipe down their trolleys.

[Sciolus]

That's because you're riff-raff. Booths have someone to do it for you.

[raven]

My first thought there was what's Richard O' Brien got to do with anything....

[Herainestold]

Here is a study which shows the dispersal of the virus when a person is walking or running. Two metres is not a safe distance in such a situation it should be many multiples of that depending on how fast the person is moving.
The bigger point is that being outside is no guarantee of safety. Probably better to forego outside exercise and stay inside!

Does anybody have any idea of what is the maximum distance at which you could still be infected? I don't even know how you could test that, but maybe if there was a case where a subject was only exposed to one person at a distance, you could estimate it.

https://medium.com/@jurgenthoelen/belgi ... df19c77d08

[AMS]

What will matter here is how much viral shedding you actually get from asymptomatic cases. I doubt whether many people will go out for a run with overt symptoms.

[Holylol]

Here is a study which shows the dispersal of the virus when a person is walking or running. Two metres is not a safe distance in such a situation it should be many multiples of that depending on how fast the person is moving.
The bigger point is that being outside is no guarantee of safety. Probably better to forego outside exercise and stay inside!

Does anybody have any idea of what is the maximum distance at which you could still be infected? I don't even know how you could test that, but maybe if there was a case where a subject was only exposed to one person at a distance, you could estimate it.

https://medium.com/@jurgenthoelen/belgi ... df19c77d08

A critic of the piece of writing (and the underlying work) that you linked to:
https://www.vice.com/en_us/article/v74a ... ly-a-study

[Herainestold]

Here is a study which shows the dispersal of the virus when a person is walking or running. Two metres is not a safe distance in such a situation it should be many multiples of that depending on how fast the person is moving.
The bigger point is that being outside is no guarantee of safety. Probably better to forego outside exercise and stay inside!

Does anybody have any idea of what is the maximum distance at which you could still be infected? I don't even know how you could test that, but maybe if there was a case where a subject was only exposed to one person at a distance, you could estimate it.

https://medium.com/@jurgenthoelen/belgi ... df19c77d08

A critic of the piece of writing (and the underlying work) that you linked to:
https://www.vice.com/en_us/article/v74a ... ly-a-study

Okay, thanks. Anybody have anything better on this topic?

I am concerned about outside infectivity as opposed to inside. Obviously some places inside are very infectious like hospitals or churches (all that singing!). What about say, supermarkets versus being outside on a walking path?

[Brightonian]

Here is a study which shows the dispersal of the virus when a person is walking or running. Two metres is not a safe distance in such a situation it should be many multiples of that depending on how fast the person is moving.
The bigger point is that being outside is no guarantee of safety. Probably better to forego outside exercise and stay inside!

Does anybody have any idea of what is the maximum distance at which you could still be infected? I don't even know how you could test that, but maybe if there was a case where a subject was only exposed to one person at a distance, you could estimate it.

https://medium.com/@jurgenthoelen/belgi ... df19c77d08

A critic of the piece of writing (and the underlying work) that you linked to:
https://www.vice.com/en_us/article/v74a ... ly-a-study

Okay, thanks. Anybody have anything better on this topic?

I am concerned about outside infectivity as opposed to inside. Obviously some places inside are very infectious like hospitals or churches (all that singing!). What about say, supermarkets versus being outside on a walking path?

This, supermarkets v surrounding streets, something I also want to know. I'm assuming surrounding streets are a lot safer on the grounds that particulates get carried away by the wind (and also it's a whole lot easier to avoid people by just stepping into the road etc.). Probably not easy to quantify, but how much safer? Would an order of magnitude be reasonable? Or just 2-3 times?

Also, on supermarket deliveries, is a delivery necessarily safer than going in person? I assume (and I think this is the case with one of my local supermarkets) that, for a delivery, a supermarket employee simply goes round the aisles with a trolley picking out my desired items. But that employee could have a casual approach to hygiene (not picking a disinfected trolley, not using gloves, licking fingers etc.).

[Herainestold]

This, supermarkets v surrounding streets, something I also want to know. I'm assuming surrounding streets are a lot safer on the grounds that particulates get carried away by the wind (and also it's a whole lot easier to avoid people by just stepping into the road etc.). Probably not easy to quantify, but how much safer? Would an order of magnitude be reasonable? Or just 2-3 times?

Also, on supermarket deliveries, is a delivery necessarily safer than going in person? I assume (and I think this is the case with one of my local supermarkets) that, for a delivery, a supermarket employee simply goes round the aisles with a trolley picking out my desired items. But that employee could have a casual approach to hygiene (not picking a disinfected trolley, not using gloves, licking fingers etc.).

Are you more likely to be infected from breathing contaminated air or from touching a contaminated surface and transferring it to your person?
If your delivered groceries are contaminated, you can always disinfect them and your self after dealing with them. At least you are not breathing the supermarket air. I really don't know and would like to know