Thread by @JamieWoodhouse, Thank you for holding the #Lockdown!So important, as ~1 in 14 [...]

Thank you for holding the

#Lockdown!

So important, as ~1 in 14 UK people (4.7 million) may have #COVID19.

Maybe 1 in 8 in London.

That means there are infected people in every park, in every shop, in every street. It might include you!

Thread w/calculations if interested:

Assume: 5,921 deaths (hospital deaths + assumed 20%)

Infection Fatality Rate (not case fatality): 1%

Adjusted days infection to death ~18

So ~592k infected up to 18 days ago

~5.7 days to double so ~3.2 doublings since

So infections to date: ~5.3m, ~11% recovered so ~4.7m now

Whole model is v.sensitive to inputs, so low confidence + wide ranges apply.

More deaths --> more infections
Higher IFR% --> fewer infs (don't need as many for same deaths)
Longer days to death --> more infs (more time to double)
Higher doubling rate --> more infs

This is a simple, top-down model.

For a pro version that also uses a "death, days to death, transmission speed" approach, read this from Imperial.

Already low given new deaths + non-hospital additions.

http://imperial.ac.uk/news/196556/coronavirus-measures-have-already-averted-120000/

h/t @StefanFSchubert

It's heartening to finally see some press references to % infected, not just the "confirmed cases" iceberg tip.

https://unherd.com/2020/04/how-likely-are-you-to-die-of-coronavirus/ @TomChivers

https://news.sky.com/story/coronavirus-the-data-suggests-the-uk-is-on-course-for-many-thousands-of-deaths-11966517

https://telegraph.co.uk/news/2020/03/29/least-16m-people-could-infected-coronavirus-uk-new-estimates/

https://metro.co.uk/2020/03/30/coronavirus-slowing-uk-thanks-social-distancing-measures-12476442/ https://msn.com/en-gb/news/newslondon/up-to-one-in-10-londoners-may-be-infected-with-coronavirus-expert-warns/ar-BB11HBdk

Up to one in 10 Londoners may be infected with coronavirus, expert warns

Up to one in ten Londoners “at the outside” may be infected by the coronavirus wave set to hit Britain, a leading expert said.

https://unherd.com/2020/04/how-likely-are-you-to-die-of-coronavirus/

Numbers would imply total UK death toll of ~53k...

But only if IFR remains 1% + we see zero new infections.

Sadly, neither of the above are sound assumptions.

If our ICU capacity is overrun, the IFR% will spike hard.

New infections depends on hard #Lockdown + test/trace.

A wave is crashing over our ICUs.

We can't reduce the size of that wave because it's caused by infections from 2-5 weeks ago.

We can improve our readiness by scaling ICUs + protecting NHS staff.

We can stop the wave getting bigger + longer by hard #Lockdown + test/trace.

It's tempting to think... "There's 5921 deaths and #Covid19 kills about 1 in 100, so there must be ~592k infections".

The problem is you're nearly right. But those ~592k infections were 2-3 weeks ago. That's how long it takes to kill.

They've been doubling every ~5-6 days since

This isn't the best way of estimating % infected!

We're waiting for people to die, assuming fatality rate to judge how many infections drove those deaths, then using doubling rates to judge infections today.

A better way? Random pop. sample testing! https://twitter.com/JamieWoodhouse/status/1243875344916111360?s=20

https://twitter.com/JamieWoodhouse/status/1243875344916111360?s=20

Why is estimating # infected more important than just tested "cases"?

Infected people are doing the infecting. The "cases" are in hospital/dead/immune

If you know # infected and # deaths you can assess how deadly this thing really is (IFR%, not just "case" fatality)

Telling public % infected helps us comply with hard #Lockdown.

BJ's speech should have started:

"There are infected people in every train, in every shop, in every park, in every tube... you might even be one of them... please take what I am about to say very seriously..."

This poll shows a dangerous level of complacency across the UK. I suspect this is worse in the real world.

Most people think less than a million are infected! That's what happens when govt + press only talk about the "confirmed cases" iceberg tip. https://twitter.com/JamieWoodhouse/status/1245291470107672576?s=20

https://twitter.com/JamieWoodhouse/status/1245291470107672576?s=20

"Total infected" tells us how many people are going to be coming through our ICU capacity in the next few weeks and whether that will be overrun.

If it is, #Covid19 will kill much more than 1%. When you run out of ICU beds / ventilators, many more die as in Italy/Spain.

If we'd started projecting total infected from day one (ideally via. regular pop. sample tests), we might have acted sooner.

We might also have persuaded people to comply better with our weak #Lockdown.

Instead... "a national scandal" @richardhorton1 https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30727-3/fulltext

Offline: COVID-19 and the NHS—“a national scandal”

“When this is all over, the NHS England board should resign in their entirety.” So wrote one National Health Service (NHS) health worker last weekend. The scale of anger and frustration is unpreced...

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30727-3/fulltext

A powerful visualisation of deadly UK #Covid19 complacency:

"Right things... at the right time..."?!?

H/t @Imperial_JIDEA

(I'll stop my amateur efforts as your weekly reports start to come out - critically important)

Amateur epidemiologists like me are annoying, but as long as we have pro epidemiologists saying things like:

"We have no way of knowing" or

"2-5x cases"... or

Refusing to even try to estimate this most critical number...

It feels sensible to have a top down sanity check.

Thanks to those rare data journalists grappling with this most critical estimate - how many are really infected.

@TomChivers @EdConwaySky @alexwickham @Ashley_J_Kirk @PaulNuki @AlbertoNardelli @nicholascecil @jburnmurdoch

Wish you were asking questions at the daily pressers!

+ Thanks to the professionals who are trying to work "true infected" out instead of dodging.

Govt (+ public) need to listen.

@Imperial_JIDEA @imperialcollege @edge_health_ @georgebatchelor @ChristianMoroy @neil_ferguson

https://edgehealth.co.uk/post/covid23march2020 https://twitter.com/Imperial_JIDEA/status/1244607618989031424?s=20

+ Final thanks as ever to @cheianov who helped improve the maths.

Particularly modelling an adjusted "infected to death" duration given exponential skew over time.

On average, deaths to date are caused more by recent deaths than the 23.5 days from infection to death implies.

#Lockdown is really hard.

But every day, more people recover. Maybe 580,000 have so far!

And every day, the strictness of our #Lockdown determines how many new people are infected.

That balance will determine whether our NHS can cope and how many lives we can save.

Thank you!

Latest Threads Unrolled: