Covid-19 and purity spirals

[DreadPirateLuna]

Covid-19 is a very serious illness which threatens our most vulnerable and risks overwhelming the NHS. We should all do what we can to flatten the curve and save lives. People whose behaviour risks lives (e.g. urban residents traveling out to holiday homes in rural communities) should face criticism and sanctions.

However, I can't help feeling that some of the outrage at some behaviours is less about reducing the spread and more about getting caught in a "purity spiral".

Take all the outrage about people in parks. Fresh air and sunshine is good for physical and mental health, it improves the immune system which is particularly important during an epidemic! Many urban residents have no other source of open space except the local park. The ability to get outside can be lifesaving for victims of DV. Risks of contracting disease are very low if you keep your distance from others outside your household.

Yet I've seen photos of walkers and family groups in parks, keeping far away from others, but accused of selfishness and killing the elderly and disrespecting the NHS. Parks in London have been closed, meaning more congestion of other areas and residents confined to homes, which is damaging for reasons outlined above.

And it's usually (though not exclusively) women and esp mothers who get blamed. Those selfish Karens and their broods.

A more sensible solution would be to allow restricted access to the parks. Maybe allow only locals in nearby flats without gardens. But it seems we're not doing sensible these days.

They don't need to get down to 2,500. It needs to come down low enough to monitor it.

How will it get from about 500 000 to 2500 though if people are still going to work, going to the shops and coming into the country? How will you know when the levels are low enough to monitor if only 10 000 people/day are being tested?

Iceland's official death rate is currently running at about 0.5%, and they reckon even with their existing extensive testing that it could be missing about half of their cases (which roughly ties in with their random study finding half are asymptomatic)

If, and it's a big if, these are closer to the true numbers then with 10,600 deaths at 0.5% that would mean the UK had over 2 million people who have had it. If they are missing about half as they suspect then you're at nearer 4.5 million. Some of those will be recovered of course (or never truly sick)

Let's say that we have even 1 million infected, and that the lower r0 estimate from the London School of Tropical Meds applies (0.62). Now, how long from infection to contagion is difficult - 1-14 day incubation period, average 6 days to onset of symptoms but many asymptomatic. I'm going to go with most being contagious at 1 week for easy maths.
If we start with 1 million infected, then in a week they will have infected 620k
2 weeks - 384k
3 weeks - 238
4 weeks - 148k
5 weeks - 92k
6 weeks - 57k
7 weeks - 35k
8 weeks - 22k
9 weeks - 13.5k
10 weeks - 8.4k
11 weeks - 5.3k
12 weeks - 3.2k - near enough Korea

Now this is a gross simplification as it assume the existing cases drop off so in reality you need to add a week or two.

That's if we start with 1 million. If we start with 2 million you can add another couple of weeks, 4.5 add another couple.

And that's assuming that we have the contagion rate as low as we think. If the level of asymptomatic cases is high then the r0 was probably underestimated in the first place and therefore the current r0 which is based on this may also be too low. If it's closer to 1 then we're going to plateau for a while.

We're so far away from having the testing capacity we need for this too.

Well, I think the only way out is test, track, trace and quarantine. I can't see people accepting just letting thousands die at home because the hospitals are overwhelmed which is what will happen if we just lift lockdown and leave it up to fate.

I called the tracking app, which has now been confirmed, despite you all accusing me of magical thinking. Time will tell if the rest of my predictions are right

I don't think it's the existance/use of an app you were accused of magical thinking over.

I think I follow! Late at night here but have a horrible heavy period.

So - best case scenario from lock down is that r0 is below 1 and the number of active infected cases is a million.

In which case there’s 3 full months of lock down minimum before lockdown could be lifted and monitoring type numbers.

But - if, as you say, there really are a whole heap of asymptomatic cases then r0 will be closer to 1 in which case things will remain at a plateau for a long time.

All of which is probably moot without testing numbers increasing 10 fold, because at present active cases are significantly underestimated and shifts in the number of cases are therefore harder to interpret.

despite you all accusing me of magical thinking.

Nothing at all to do with the app, but you know that.

Hope everyone is enjoying their essential wine and chocolate!

We all want the same thing: to get out of this nightmare situation with as few deaths as possible.

I'm actually quite impressed with how well the British public are adhering to restrictions. Despite the past six weeks of conflicting messages, despite the years of being told there's no such thing as society and our only worth is as consumers, it seems that when push comes to shove, 90+% of Brits will accept severe restrictions on their lives in order to protect the vulnerable. Even where people are going against guidelines, it's often a case of confusion or ignorance rather than malice, and education is a better tool than anger.

And yet the current media narrative is that we're all a bunch of evil sunbathers and toilet roll hoarders who are going to kill grannies and nurses with our selfishness and need to be locked in our homes for our own good.

This is a dangerous message for two reasons:

• It detracts attention away from the people who actually let us down. (Shades of Hillsborough and Grenfell Tower)
• It risks becoming a self-fulfilling prophecy, as people are less likely to comply if they believe their neighbours aren't doing so.

Look at countries with lower case loads and deaths than Britain, despite being close to the epicenter in Europe. Do you really believe that the Germans, Greeks and Irish are just better people than the naughty Brits? Or are they lucky enough to have leaders who took this seriously, shut down early, and communicated clearly with their citizens?

Bleurgh to heavy period. Don't the little buggers understand we can't readily access our preferred take out/chocolate survival supplies?

That's my back of a fag packet analysis of the numbers. In reality I think they will be aiming to maintain that number at a level where the number of active cases is such that the critical care capacity isn't exceeded.

it seems that when push comes to shove, 90+% of Brits will accept severe restrictions on their lives in order to protect the vulnerable.

I don't think that's the driving force at all. I've seen too many comments on MN along the lines of " why are we doing this to protect people who were going to be dead within a year anyway" to buy into the altruistic rhetoric. I'm sure many people are doing it to protect either themselves or a family member who they know are at risk.

Let's see the levels of altruism when we have to start weighing competing needs.

Just clocked something in the BBC description of the app

"At present, the idea is that people who have self-diagnosed as having coronavirus will be able to declare their status in the app.

The software will then send a "yellow alert" to any other users who they have recently been close to for an extended period of time.

If a medical test confirms that the original user is indeed infected, then a "red alert" will be sent instead, signalling that the other users should go into quarantine."

So you won't be told to go to quarantine unless it's confirmed, but will be notified if it's suspected. I could see that changing if the testing volumes aren't ramped up drastically

mobile.twitter.com/natesilver538/status/1249373172690046977/photo/1

FWIW the IHME is predicting another 37 000 deaths in the U.K. in the next (just under) 4 months. Which seems high, wonder what their modelling is based on.

It would be interesting to know as over that period they will HAVE to have built in assumptions about lockdown.

I think it tries to incorporate lockdown (or not) population density, hospital and intensive care/ventilator capacity.

Actually, I might be misinterpreting but I think the figure is total first wave deaths - including those who have died already. So a further roughly 27k.

These numbers aren't very believable though; Italy is close to that number already and whilst they are declining it seems unlikely they'll hit that target. I do note however that it's specifically called first wave deaths - I don't know when they might be predicting wave 2 for Italy.

That modelling is being slated though so wouldn't hold much store by it

The IHME were saying 66,000 at the beginning of last week and have almost halved it since. Interestingly, they're also saying that Italy will have 20,000 in total in this first wave. The numbers in Italy are dropping but they're currently at 19,650 with many people still in hospital so that seems a little off as well.

Actually, I might be misinterpreting but I think the figure is total first wave deaths - including those who have died already. So a further roughly 27k.

No you’re right, I misread. It’s an “as of through to” number, not a “from” number.

A further 27 thousand doesn’t seem that extreme then.

Every model is being slated from what I've seen

Hooves, I actually believe getting the numbers lower to allow for contact tracing could be a feasible strategy but one question I have not yet seen you answer is: How do you want to get the number low enough for that to become a possibility while borders/non-essential businesses remain open? No policing of people's shopping habits is ever going to compensate for the mixing that's still happening at the airports, Amazon warehouses etc.

Liking your numbers Statistically
Always loved your analyses. Glad to see you here

Indyrefer Dances?

I'll admit I find the modelling problem that this poses quite interesting (I do similar work but in a different field)

fivethirtyeight.com/features/best-case-and-worst-case-coronavirus-forecasts-are-very-far-apart/

This article was interesting statistically, pointed out that intuition and intuition was relied heavily on for modelling predictions.

Sorry, intuition and experience!

I'm not sure I really understand this assumption that we will be able to do something.

I do think there are actions governments and people can take that will help and we should try to manage it without avoidable loss of life. But it could easily be the case that what we can do is limited and will never be all that successful. It's a natural disease and like many natural diseases it will run its course and infect and kill people.

There are many many diseases like this that kill people every year, and there is nothing we can do. Having made progress with many does not mean we will always make the progress we would like in the future. When we fail, we don't shut down life indefinitely, we learn to live with it. We could quarantine society forever and I imagine many scourges would go down in frequency, from flu to lice to chlamydia. But there is no way people are going to stop going about the business of life in the long term to achieve that. People as a whole accept infestation, infection, and death every day. In many ways I think they find it easier than accepting society shutting itself up.

Expert judgement - which is basically intuition and experience - is a huge component of these sort of complex models. It has to be as the current data can only tell you so much.

Even where the current data is solidly factual - e.g. a current market price of an actively trading stock - then it only gives you data for there and then. You've then got to model the evolution which requires a whole series of assumptions. Most of the time they will be based upon data; some will be based on a historical time series for example. But there's always an overlay of judgement to this - do we use the full data set, as some of it corrupot, how should we weight it - but then also the consideration of whether the past is a good representation of the future. Then you've got to consider correlations - how does X change when Y changes, is the relationship constant and so on.

When we're talking about modelling C19 the starting numbers aren't even solidly factual. Look at the range of possible estimated for death stats alone - ranging from well under 1% up to about 13% as overall average case fatality rates. We don't know how many infected people there are...so trying to model how it evolves is very challenging.

It's easy to snipe at models - and I was guilty of it myself earlier - but the complexity is not easy and the level of uncertainty when you're dealing with such a new virus makes it challenging. They'll be using stochastic models to understand a range of possible outcomes but I'd expect the ranges to be pretty wide.