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Coronavirus - General Chat - No statistics

The home for all non-political Coronavirus (Covid-19) discussions on The Lemon Fool
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This is the home for all non-political Coronavirus (Covid-19) discussions on The Lemon Fool
swill453
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Re: Coronavirus - General Chat - No statistics

#432887

Postby swill453 » August 6th, 2021, 12:24 pm

Interesting article in Wired about the airborne transmission of Covid (and other diseases) https://www.wired.com/story/the-teeny-t ... ovid-kill/

It turns into a bit of a medical history detective story, and shows that the "5 microns = aerosol" rule-of-thumb is based on a misreading of literature.

Scott.

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Re: Coronavirus - General Chat - No statistics

#432889

Postby servodude » August 6th, 2021, 12:33 pm

swill453 wrote:Interesting article in Wired about the airborne transmission of Covid (and other diseases) https://www.wired.com/story/the-teeny-t ... ovid-kill/

It turns into a bit of a medical history detective story, and shows that the "5 microns = aerosol" rule-of-thumb is based on a misreading of literature.

Scott.


Isn't one of those "let's make it binary" things that appeals to those wanting a simple taxonomy?
- which is fine in any specific context but ultimately dangerous if you think your arbitrary lines have any bearing in the real world

(as opposed to the spinach == iron typo?)

-sd

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Re: Coronavirus - General Chat - No statistics

#433072

Postby 88V8 » August 7th, 2021, 9:56 am

swill453 wrote:Interesting article in Wired about the airborne transmission of Covid

What a perfect example of 'silos' and the establishment circling the wagons. A facet of human nature that will never ever change.

Really have to admire Marr for her persistence.
I made a fuss last winter about ventilation, but no one in the media or the govt seemed to take the slightest notice, so I thought 'huh' or words to that effect, and gave up.

Hats off to her.

V8

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Re: Coronavirus - General Chat - No statistics

#434297

Postby Julian » August 12th, 2021, 11:01 am

At last! ....

Air purifiers trialled in UK schools in plan to keep pupils safe from Covid-19
...
Thirty primary schools in Bradford are taking part in the Government-funded research project, which could be scaled up to operate nationwide depending on the evidence produced.

If the devices are found to work, the study could deliver a “massive prize” in the fight against Covid, while also cutting absences because of cold and flu and improving the air quality for pupils with asthma and hay fever.
...


[ Source: https://inews.co.uk/news/air-purifiers- ... id-1146965 ]

A few people here have bemoaned the way the focus on "hands, face, space" totally ignored any messaging regarding ventilation but another bugbear of mine throughout much of this pandemic has been the seemingly very little discussion of how the indoors might be made at least somewhat more like the outdoors in terms of being a less hospitable environment for SARS-CoV-2 to spread in.

This air purification route might be a dead end - things like equipment cost, overly onerous requirements for frequent filter changes, increases in background noise levels or simply that it is impractical to turn/scrub a given volume of air enough times per hour to have any useful effect could make this impractical but it's nice to see that we have at least got to the stage of doing some practical research on the possibilities here.

If we are to believe those experts who are telling us that this is unlikely to be the last pandemic in our lifetimes(*) then our responses now should not be confined to getting through this pandemic but where possible also to leave some infrastructure in place to potentially help reduce the impact of whatever might hit us next. General improvements in indoor air quality, if achievable, would seem to me to be a useful tool against any future airborne virus and leaves me wondering whether the widespread use of such equipment might have reduced the amount of time that hospitality venues needed to remain closed over the last 18 months with the economic and social benefits that would have delivered.

I suppose that one fly in the ointment regarding widespread deployment of such equipment is that, since electricity is needed to power such equipment, it is heading in the opposite direction of travel as far as climate change and reducing energy consumption is concerned. Hopefully increasing use of green energy can make that less of an issue going forward.

- Julian

(*) A fairly ridiculous way to specify a timescale since lifetimes vary hugely depending on an individuals current age and health but it is a phrase often used in this context.

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Re: Coronavirus - General Chat - No statistics

#434331

Postby Hallucigenia » August 12th, 2021, 1:01 pm

About $^&*ing time, this is an easy win that should have been happening over a year ago when the importance of aerosols became apparent. They should have gone round every classroom before the end of term with a CO2 meter to identify the ones with the worst ventilation and then get as many as you can up to HEPA levels of filtration over the summer holidays 2020. CO2 not a perfect proxy but it gives you a reasonable idea where to prioritise.

It's not that expensive - portable ones plus enough filters to last a few years work out at around £10/child, the maintenance is little different to replacing lightbulbs. With 8.9m schoolkids in the UK it's of the order of £10bn to put a portable HEPA filtration in every classroom in the country - not nothing, but not crazy either. And even DIY solutions like "Corsi boxes" hacked together using MERV13/F7 filters will eliminate ~75% of infectious particles for around £30. Not perfect, but it helps.

You can imagine in future that building regulations will require new "essential buildings" like supermarkets to maintain eg 2 airchanges/hour with HEPA filtration or UV during normal times, with the capacity to crank it up to 6-8 airchanges per hour during the flu season and pandemics.

Interestingly my GP surgery now has a filter unit which I'm pretty sure wasn't there a year ago - again, that's the sort of place that should have had them anyway.

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Re: Coronavirus - General Chat - No statistics

#434491

Postby daveh » August 13th, 2021, 9:23 am

Hallucigenia wrote:About $^&*ing time, this is an easy win that should have been happening over a year ago when the importance of aerosols became apparent. They should have gone round every classroom before the end of term with a CO2 meter to identify the ones with the worst ventilation and then get as many as you can up to HEPA levels of filtration over the summer holidays 2020. CO2 not a perfect proxy but it gives you a reasonable idea where to prioritise.

It's not that expensive - portable ones plus enough filters to last a few years work out at around £10/child, the maintenance is little different to replacing lightbulbs. With 8.9m schoolkids in the UK it's of the order of £10bn to put a portable HEPA filtration in every classroom in the country - not nothing, but not crazy either. And even DIY solutions like "Corsi boxes" hacked together using MERV13/F7 filters will eliminate ~75% of infectious particles for around £30. Not perfect, but it helps.

You can imagine in future that building regulations will require new "essential buildings" like supermarkets to maintain eg 2 airchanges/hour with HEPA filtration or UV during normal times, with the capacity to crank it up to 6-8 airchanges per hour during the flu season and pandemics.

Interestingly my GP surgery now has a filter unit which I'm pretty sure wasn't there a year ago - again, that's the sort of place that should have had them anyway.


How will the filters be changed safely. Our biological safety cabinets working at Cat. 2 with Class 2 or below agents require fumigation before any one can work on the HEPA filters (and its a real pain to do as the fumigant is nasty and needs careful handling) bearing in mind that Sars-cov2 is considered a Class 3 agent.

88V8
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Re: Coronavirus - General Chat - No statistics

#434511

Postby 88V8 » August 13th, 2021, 10:46 am

daveh wrote:How will the filters be changed safely. Our biological safety cabinets working at Cat. 2 with Class 2 or below agents require fumigation before any one can work on the HEPA filters (and its a real pain to do as the fumigant is nasty and needs careful handling) bearing in mind that Sars-cov2 is considered a Class 3 agent.

Well you can be sure that someone is even now thinking of ways to complicate a simple process.
The virus largely dies on crinkly surfaces in 48 hours, so Monday morning before school opens, pair of gloves, pop the old filter in a bag.

We have two dehumidifiers, not quite the same thing, but they have a filter and there is a recommended 6 month interval.
We've had them 8 years, and have never changed the filters.
Occasionally I gently back-vacuum them.
They still work fine.
Filters... the printer ink of air purifiers.

V8

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Re: Coronavirus - General Chat - No statistics

#434515

Postby Hallucigenia » August 13th, 2021, 11:00 am

daveh wrote:How will the filters be changed safely. Our biological safety cabinets working at Cat. 2 with Class 2 or below agents require fumigation before any one can work on the HEPA filters (and its a real pain to do as the fumigant is nasty and needs careful handling) bearing in mind that Sars-cov2 is considered a Class 3 agent.


If pathogen levels in a classroom are comparable to inside a safety cabinet then we've got more problems than just the filters.

Obviously one can't downplay COSHH, although it's worth noting that SARS2 is one of the organisms in a grey area between CL2 and CL3, most lab testing is allowed at effectively CL2. The one thing on our side is that in general viruses - and in particular enveloped RNA viruses like SARS2 - lose viability very quickly on surfaces, particularly dry porous surfaces like HEPA filters. Greatorex et al showed that flu virus loses viability within 4 hours on most surfaces, including J-cloth which is a reasonable proxy for HEPA filters.

van Doremalen et al in an early study found SARS2 survived up to 24h on cardboard, rather more than SARS1, but "Estimated differences in half-life between the two viruses were small except for on cardboard (Figure 1C, Table S1). Individual replicate data were noticeably noisier for cardboard than other surfaces (Figures S1–S5), so we advise caution in interpreting this result."

We're not talking something like anthrax which is super-persistent. Combine that with the fact that we have a good vaccine and the obvious thing to do is just wait until the end of school holidays to change filters. But away from schools, I'd suggest the following is defensible :

Vaccinated
48h after room was last used (eg after weekend)
Mask & gloves
Move portable appliances outside if practical

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Re: Coronavirus - General Chat - No statistics

#434535

Postby daveh » August 13th, 2021, 11:48 am

Thanks for the papers Hallucigenia, from reading through them it looks like you could argue that changing the filters after a short quarantine period (for the machinery) whilst wearing appropriate PPE (gloves/ mask?) should be fine.

I wonder how frequently the HEPA filters would require changing. Our safety cabinets are regularly tested for performance and serviced, but we've never needed to change the filters on our present cabinets and only once in our previous cabinet after 10 years of use.

I wouldn't expect large quantities of pathogens in most of our safety cabinets either, they provide operator protection but are mostly to protect the work from contamination (from air born bacteria and yeasts) as I'm mostly doing tissue culture and I shouldn't be producing much in the way of aerosols. But I do find that health and safety can be overly risk averse at time.

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Re: Coronavirus - General Chat - No statistics

#434555

Postby Hallucigenia » August 13th, 2021, 12:31 pm

daveh wrote:I wonder how frequently the HEPA filters would require changing. Our safety cabinets are regularly tested for performance and serviced, but we've never needed to change the filters on our present cabinets and only once in our previous cabinet after 10 years of use.


Usual manufacturer guidelines seem to be annually. It feels like there's an element of the printer-ink scam in that, but schools will do things by the book.

daveh wrote:I wouldn't expect large quantities of pathogens in most of our safety cabinets either, they provide operator protection but are mostly to protect the work from contamination (from air born bacteria and yeasts) as I'm mostly doing tissue culture and I shouldn't be producing much in the way of aerosols. But I do find that health and safety can be overly risk averse at time.


I must admit, I wasn't aware of fumigation being needed when I was using flow hoods, even when playing with some reasonably interesting pathogens, but it's not something I ever asked about. Obviously it depends a lot on the pathogen and the environment - SARS2 is a lot scarier in August 2020 than it is in August 2021 due to the vaccine, and you can catch it in Tesco whereas some of our bugs were not present in the UK and we needed to keep it that way. Also if there's one lab playing with dangerous stuff, they're going to have to get the fumigators out anyway, so they'll tend to apply the same treatment to all areas.

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Re: Coronavirus - General Chat - No statistics

#434580

Postby daveh » August 13th, 2021, 2:44 pm

Hallucigenia wrote:
I must admit, I wasn't aware of fumigation being needed when I was using flow hoods, even when playing with some reasonably interesting pathogens, but it's not something I ever asked about. Obviously it depends a lot on the pathogen and the environment - SARS2 is a lot scarier in August 2020 than it is in August 2021 due to the vaccine, and you can catch it in Tesco whereas some of our bugs were not present in the UK and we needed to keep it that way. Also if there's one lab playing with dangerous stuff, they're going to have to get the fumigators out anyway, so they'll tend to apply the same treatment to all areas.


The reason I know about the fumigation is because I had to do it for our previous biological safety cabinet when it required a filter replacement. We used formaldehyde in an atomiser. Then had the problem of making sure the room and cabinet were safe ie no traces of formaldehyde left in the room before anyone could use the room.

When we have the cabinets serviced we have to provide a certificate to say,
1) The cabinet was fumigated on ..... and has not ben used subsequently
or
the cabinet has not been used for pathogens in hazard group 2 or above since last fumigated
or
3) the cabinet has been used for for pathogens in hazard group 2 and has not been fumigated. It is understood that no work will be required on the filters or the interior of the cabinet (eg air ducts) and cabinet surfaces will be wiped down with disinfectant

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Re: Coronavirus - General Chat - No statistics

#434628

Postby Hallucigenia » August 13th, 2021, 8:04 pm

This new preprint from Maryland only had 4 people with alpha (B1.1.7, "Kent") in their study but FWIW :

alpha variant infection was associated with a 100-fold (95% CI, 16 to 650-fold) increase in coarse - and a 73-fold (95% CI, 15 to 350-fold) increase in fine-aerosol RNA shedding... Fine-aerosol shedding remained significantly greater for alpha variant infections (18-fold, 95% CI, 3.4 to 92-fold)...alpha variant infection was associated with a 100-fold (95% CI, 16 to 650-fold) increase in coarse- and a 73-fold (95% CI, 15 to 350-fold) increase in fine-aerosol RNA shedding...

We observed statistically significant reductions in aerosol shedding [when wearing masks]...: 77% (95% CI, 51% to 89%) reduction for coarse and 48% (95% CI, 3% to 72%) for fine aerosols (Figure 1)...mask performance was not significantly different for alpha variant infections...We did not observe a significant difference between surgical masks and a composite of the various cloth masks studied....

Seropositive cases tended to cough more than seronegative cases...


They detected infectious virus in 68% of nostril and 32% of saliva samples, but the only infectious virus in 141 samples of fine aerosol came from 2 patients, one with alpha and one with 20G, a "Californian" variant related to the somewhat more transmissible epsilon.

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Re: Coronavirus - General Chat - No statistics

#434740

Postby 88V8 » August 14th, 2021, 12:48 pm

Hallucigenia wrote:We observed statistically significant reductions in aerosol shedding [when wearing masks]...:
We did not observe a significant difference between surgical masks and a composite of the various cloth masks studied....

That's interesting.
Considering that many people suggest masks make little difference.

And the cloth/3-ply. Surprised at that.

Waitrose this morning, all masked.

V8

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Re: Coronavirus - General Chat - No statistics

#434741

Postby pje16 » August 14th, 2021, 12:57 pm

88V8 wrote:Waitrose this morning, all masked.

Tesco yesterday all masked
Got told by somebody who went to Asda - no masks
make of that what you will :roll:

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Re: Coronavirus - General Chat - No statistics

#434747

Postby Itsallaguess » August 14th, 2021, 1:09 pm

pje16 wrote:
88V8 wrote:
Waitrose this morning, all masked.


Tesco yesterday all masked

Got told by somebody who went to Asda - no masks

make of that what you will :roll:


After taking the view that I'd continue to wear a mask whilst supermarket shopping primarily as a sign of respect for those that have to work there (I've been double-jabbed for a while now, and have no huge issues with the risk of catching it myself), I've been quite disappointed to see that the majority of the people I see wearing masks in the Morrisons that I go to have been the shoppers themselves, with hardly any of the staff wearing masks at all...

I'll continue to wear mine whilst doing my weekly shop, but the reason I'm doing so has been somewhat diluted by the actions of the people I was actually trying to be considerate of, I've got to say...

Cheers,

Itsallaguess

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Re: Coronavirus - General Chat - No statistics

#434751

Postby redsturgeon » August 14th, 2021, 1:22 pm

Itsallaguess wrote:
pje16 wrote:
88V8 wrote:
Waitrose this morning, all masked.


Tesco yesterday all masked

Got told by somebody who went to Asda - no masks

make of that what you will :roll:


After taking the view that I'd continue to wear a mask whilst supermarket shopping primarily as a sign of respect for those that have to work there (I've been double-jabbed for a while now, and have no huge issues with the risk of catching it myself), I've been quite disappointed to see that the majority of the people I see wearing masks in the Morrisons that I go to have been the shoppers themselves, with hardly any of the staff wearing masks at all...

I'll continue to wear mine whilst doing my weekly shop, but the reason I'm doing so has been somewhat diluted by the actions of the people I was actually trying to be considerate of, I've got to say...

Cheers,

Itsallaguess


I guess there is a huge difference in comfort/inconvenience between wearing a mask for 20 minutes while shopping and wearing one for a full 8 hour shift.

John

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Re: Coronavirus - General Chat - No statistics

#434754

Postby Hallucigenia » August 14th, 2021, 1:29 pm

Also masks cost money, and if you're on min wage then you may feel that other calls on your money have greater effects on your health, like not being homeless.

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Re: Coronavirus - General Chat - No statistics

#434759

Postby pje16 » August 14th, 2021, 1:56 pm

redsturgeon wrote:I guess there is a huge difference in comfort/inconvenience between wearing a mask for 20 minutes while shopping and wearing one for a full 8 hour shift.

I had a chat with a friendly woman on the checkout at Tesco and that's exaclty what she said
"I'm behind the plastic screen anyway and not close to customers" - I had to agree
I still wear mine, like you said 20-25 mins is no big deal, and give people something to smile about as I have a range of funny ones :D

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Re: Coronavirus - General Chat - No statistics

#434765

Postby Itsallaguess » August 14th, 2021, 2:53 pm

Hallucigenia wrote:
Also masks cost money, and if you're on min wage then you may feel that other calls on your money have greater effects on your health, like not being homeless.


Of course - and if any masks that people might be hoping that supermarket employees might continue to wear would have to be paid for by those employees, then it would be understandable that there's an additional pressure there that might prevent them doing so.

I suppose my criticism in that situation would have to be with the supermarkets for not providing them free for any employee that might wish to continue wearing them if they wish to do so.

I only mentioned this aspect as being slightly disappointing, as I was hoping there might have been more of a collective effort in those types of situations, and that would of course mean employers efforts too...

I also agree that if they are behind the plastic screens, then that removes the issue to some extent - it was the many employees walking around the store, such as the online shopping squads, that were mostly mask-free in a way that initially surprised me...

Cheers,

Itsallaguess

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Re: Coronavirus - General Chat - No statistics

#434771

Postby 9873210 » August 14th, 2021, 3:26 pm

88V8 wrote:
Hallucigenia wrote:We observed statistically significant reductions in aerosol shedding [when wearing masks]...:
We did not observe a significant difference between surgical masks and a composite of the various cloth masks studied....

That's interesting.
Considering that many people suggest masks make little difference.


"statistically significant" and "clinically significant" are not the same thing.

Statistical significant is a useful, and I don't expect any single paper to do all the work, but additional data (or deductions) are needed.


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