Covid (3/n)
Mar. 16th, 2020 08:46 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
jackI've read a lot of persuasive contradictory articles about the current situation and I think I'm finally fitting them together into some sort of shape.
Look at numbers. Out of a 1000 people in a country like the UK. If they all get infected, estimates I'm seeing guess that 80% of people will experience a cold or mild flu that they recover from on their own (so even in the worst predictions, we should be able to make deliveries keep coming). 15% will experience bad flu, but recover. 5% will need need serious hospitalisation, 1% will die even with a hospital.
For 1000 people, there are 2 hospital beds. And less than 0.1 ventilators, which most people hospitalised will need.
If the infection isn't contained (either grows unchecked as in some countries, or slow growth as in countries that have it sort of contained but not eliminated), then something like 80% of people will get it depending on how effective measures are taken. But those hospital beds and ventilators are ALREADY FULL. So I'm going to temporarily not think about both those things and just pretend that on average everyone gets it.
Then, out of 1000 people, 50 need treatment, in one of those 0.1 ventilators. For two weeks or more likely a month. So if we "flatten the curve" enough to treat everyone who needs it, the situation will go on for forty years.
The death rate for over 70s is more like 10%-20% and the death rate for younger people is more like 0.2%. I assume the hospitalisation rates follow a similar proportion. If everyone who's vulnerable is kept safely isolated, that might reduce the numbers above by a factor of 5. So... less than a decade. Maybe more if we got serious about protecting everyone who was vulnerable.
So when we talk about three months, that could mean, "we successfully contained it, almost everyone infectious has stopped spreading it, the rates are all going down". Or it could mean, "it's run through the whole population". Those are quite different pictures. But I and maybe a lot of people weren't thinking about that.
But surely...
I really really hope that those numbers above don't come to pass. Plausibly we'll reach the same point as China "we should have contained it earlier, but now we're going to contain it as much as possible". If the situation drags on another year, hopefully we WILL manufacture 10x or 100x the number of ventilators. And find a vaccine. And realise which containment measures help and which just make people sad but don't help.
On Thursday it seemed like the government was ignoring this. On Friday they hinted they'd get serious about helping protect vulnerable people. On Sunday they said they would, and also started saying, "hey can we maybe get some war-footing ventilator production." Today I'm hearing, "the situation might last until next year." We should have been doing some of that planning three months ago, but I admit I wasn't thinking about it then either. So hopefully, even if the politicians are a bit bumbling, they HAVE been taking the advice from the epidemiologists, so they will do the right things, even if a bit inconsistently and late. Hopefully they will also not react TOO much (e.g. "banning going outside" is probably counterproductive, encourage walks, discourage gathering).
Those articles
"Flatten the curve". This says, spreading out the infection reduces the load at once on the health care system. Which is true. But (probably deliberately, to avoid getting people to despair), it didn't mention that in some cases, that might mean, "reducing 100s of people per ICU bed to 50s of people per ICU bed".
"The curve is a lie" Several people wrote angry articles pointing out the flaw in the curve theory.
"Herd immunity something" Talking about, if it does spread unchecked
"Act NOW!" My instinct would be act now to contain the problem when it's as small as possible, in the hopes of finding the best lockdown politicy to eliminate it while still allowing normal life to continue, expanding hospital capacity, giving time for other breakthroughs. But it's also true, knee-jerk "lock down the entire country" probably isn't correct.
"Choose the right time to act" Pointing out that "act now" is wrong if you want to soften the peak rather than slow the growth. But maybe not emphasising that that would soften it only a small proportion.
I think I misread a lot of these articles through not seeing what they weren't saying.
I think a lot of people knew all this already but weren't laying it out like that, but I think a lot of people didn't understand that.
What are you doing?
I'm not that scared for me, but I'm doing what I can to slow the spread (if at some point I will get it and have several days of being infectious without knowing) because I can do so without much hardship and I think that's the socially responsible thing. I don't know if that's right, maybe that doesn't help. Probably in a week or two, we'll know which scenario we're in :(
Look at numbers. Out of a 1000 people in a country like the UK. If they all get infected, estimates I'm seeing guess that 80% of people will experience a cold or mild flu that they recover from on their own (so even in the worst predictions, we should be able to make deliveries keep coming). 15% will experience bad flu, but recover. 5% will need need serious hospitalisation, 1% will die even with a hospital.
For 1000 people, there are 2 hospital beds. And less than 0.1 ventilators, which most people hospitalised will need.
If the infection isn't contained (either grows unchecked as in some countries, or slow growth as in countries that have it sort of contained but not eliminated), then something like 80% of people will get it depending on how effective measures are taken. But those hospital beds and ventilators are ALREADY FULL. So I'm going to temporarily not think about both those things and just pretend that on average everyone gets it.
Then, out of 1000 people, 50 need treatment, in one of those 0.1 ventilators. For two weeks or more likely a month. So if we "flatten the curve" enough to treat everyone who needs it, the situation will go on for forty years.
The death rate for over 70s is more like 10%-20% and the death rate for younger people is more like 0.2%. I assume the hospitalisation rates follow a similar proportion. If everyone who's vulnerable is kept safely isolated, that might reduce the numbers above by a factor of 5. So... less than a decade. Maybe more if we got serious about protecting everyone who was vulnerable.
So when we talk about three months, that could mean, "we successfully contained it, almost everyone infectious has stopped spreading it, the rates are all going down". Or it could mean, "it's run through the whole population". Those are quite different pictures. But I and maybe a lot of people weren't thinking about that.
But surely...
I really really hope that those numbers above don't come to pass. Plausibly we'll reach the same point as China "we should have contained it earlier, but now we're going to contain it as much as possible". If the situation drags on another year, hopefully we WILL manufacture 10x or 100x the number of ventilators. And find a vaccine. And realise which containment measures help and which just make people sad but don't help.
On Thursday it seemed like the government was ignoring this. On Friday they hinted they'd get serious about helping protect vulnerable people. On Sunday they said they would, and also started saying, "hey can we maybe get some war-footing ventilator production." Today I'm hearing, "the situation might last until next year." We should have been doing some of that planning three months ago, but I admit I wasn't thinking about it then either. So hopefully, even if the politicians are a bit bumbling, they HAVE been taking the advice from the epidemiologists, so they will do the right things, even if a bit inconsistently and late. Hopefully they will also not react TOO much (e.g. "banning going outside" is probably counterproductive, encourage walks, discourage gathering).
Those articles
"Flatten the curve". This says, spreading out the infection reduces the load at once on the health care system. Which is true. But (probably deliberately, to avoid getting people to despair), it didn't mention that in some cases, that might mean, "reducing 100s of people per ICU bed to 50s of people per ICU bed".
"The curve is a lie" Several people wrote angry articles pointing out the flaw in the curve theory.
"Herd immunity something" Talking about, if it does spread unchecked
"Act NOW!" My instinct would be act now to contain the problem when it's as small as possible, in the hopes of finding the best lockdown politicy to eliminate it while still allowing normal life to continue, expanding hospital capacity, giving time for other breakthroughs. But it's also true, knee-jerk "lock down the entire country" probably isn't correct.
"Choose the right time to act" Pointing out that "act now" is wrong if you want to soften the peak rather than slow the growth. But maybe not emphasising that that would soften it only a small proportion.
I think I misread a lot of these articles through not seeing what they weren't saying.
I think a lot of people knew all this already but weren't laying it out like that, but I think a lot of people didn't understand that.
What are you doing?
I'm not that scared for me, but I'm doing what I can to slow the spread (if at some point I will get it and have several days of being infectious without knowing) because I can do so without much hardship and I think that's the socially responsible thing. I don't know if that's right, maybe that doesn't help. Probably in a week or two, we'll know which scenario we're in :(
no subject
Date: 2020-03-16 12:30 pm (UTC)no subject
Date: 2020-03-16 12:58 pm (UTC)5% or 6% requiring hospitalisation, 3% on the 'critical' list, which means intensive care and a ventilator for most of them.
If blood oxygen perfusion is available, as it was in China outside Wuhan, the expected 2% death rate is halved to 1%.
If US standards of high-dependency intensive care are available, then that 1% might actually be the norm: but we don't really know that, yet.
The joker in the statistical deck is that you might have a population where the elderly have been isolated successfully; or just haven't been caught, yet, in the early stages of the outbreak; or maybe (like Washington State) you have early-stage statistics skewed by an outbreak in a nursing home.
Hospital admission rates for the over-70's are outside my competence: but the 'off work and in bed' fraction of under-50's cannot be true of people who are over 70 and frail enough that there are no 'minor' illnesses.
You're dead right, though, about need for 'flattening' and the effects of saturating local health are resources.
no subject
Date: 2020-03-20 09:30 am (UTC)no subject
Date: 2020-03-21 09:18 am (UTC)However, Imperial College are using those numbers as the static baseline for a more challenging analysis: the population dynamics of an epidemic. That is to say: a forecast of rates of spread and the changing load, on given days, on hospital facilities.
Once the 'critical' case load exceeds ICU capacity by 2x, ventilators cease to matter and the 3% of critical cases die.
Push it further, towards that 10x factor, and we start losing the 'standard hospital bed' interventions of high-dosage anti-inflammation meds, antibiotics for secondary infections, inhaled oxygen, and all the things trained nurses can do to support a severely-ill patient.
Note that general hospital care degrades under excessive load, but doesn't have the sharp cutoff of 'No ventilator'.
Recovery rates and fatality rates are very hard to estimate in those circumstances: a hospital with patients in the corridors on trolleys and the staff dead on their feet is still a working hospital.
A hospital with patients unattended due to the staff being overwhelmed isn't.
I am worried, and I hope that it is a reflection of my inadequacies as an amateur researcher, that the Chinese case series from February 27th is still the only good baseline for morbidity and mortality.
It is, of course, rigorous work by competent researchers on a large statistical population, in a country with an advanced healthcare system, in the *only* country to have observed an epidemic of COVID-19 from end to end.
Everyone else has either controlled it all the way down to sporadic cases managed by testing, follow-up, and selective isolation; or they are in the early- or middle- stages an out-of-control epidemic.
no subject
Date: 2020-03-22 11:32 am (UTC)But what I heard was, the paper being updated with numbers from Italy which changed the recommendation from "minimising deaths by timing the shut down best relative to the inevitable peak" to shutting down earlier. I didn't understand what change would cause that change in recommendation. If the prediction was hospitals being overwhelmed either way, but talking about best ways to minimise that, surely that still applies if the deaths are higher?
I also feel like I miss something in that people referring to that minimisation strategy seem to be implicitly assuming that extra time won't help buy time for research, manufacturing masks or ventilators, more effective social distancing strategies, etc, etc. I don't know if it's just that that's futile but they don't want to say so. Or if they reached that conclusion by a different route. Or something else.
no subject
Date: 2020-03-22 04:24 pm (UTC)To be precise: very few analyses step outside the simplicity of static assumptions.
However, the picture right now is that only China added enough new ICU capacity to matter. Everyone else is either managing the outbreak well (and probably does have a successful equipment program well underway), or is one of the complacent places that neither slowed the spread nor got extra ventilators in.
Static modelling works.
no subject
Date: 2020-03-17 07:02 am (UTC)Try 3.7% - from here, which still doesn't account for the thousands of people who have been ill and recovered and never got counted.
https://informationisbeautiful.net/visualizations/covid-19-coronavirus-infographic-datapack/
no subject
Date: 2020-03-21 08:50 am (UTC)It represents the death rate without intensive care beds (read: no ventilators) and severely-reduced care in hospitals.