It's great we're flattening the curve but what if it doesn't go back down?

If every happy recovery is replaced by a new infection (R of ~1)...

We could be stuck on a plateau - with a rolling few million people infected, causing 1-2,000 deaths every day for months.

1/ Thread:

First, the optimistic evidence.

Symptom self-report indicates #Lockdown might have reduced # infections by 70% since peak of 1 Apr.

https://covid.joinzoe.com/data 

Still implies ~1.5-2m total infected so way too early to ease lockdown - but good trend!

@timspector @Join_ZOE

2/

Next, the charts. Just visually, Italy, Spain, France (and Iran) have seen flattening and a gentle reduction from peak, but then maybe plateaus rather than strong reductions?

Based on this tracker, UK response is still less stringent than Fr/It:
https://www.bsg.ox.ac.uk/research/research-projects/coronavirus-government-response-tracker

3/

UK lockdown weaker than It/Sp/Fr, but they're still seeing cases rise. Doubled in last 17-22 days ( @OurWorldInData).

Need to remove "recoveries" to estimate live infection levels, but likely flat rather than lowered?

UK doesn't report recoveries!, so can only model these.

4/

UK case growth has dropped since #Lockdown, but now stuck at ~5-6% per day. Why would it reduce further now we're a month into lockdown?

I hope doing more testing is hiding a real further slowing.

Also, we are nearing point where daily recoveries should offset new cases.

5/

That still implies we're holding the real number of infections but haven't yet begun to reduce it.

Deaths are more reliable (although understated by 1.5-2x given non-hosp / reporting lags / undiagnosed) - but lagged in time.

Also stubbornly stuck at ~6% daily increase.

6/

Most important data is the true % infected.

Random pop sample testing could tell us in days. Govt say they've been doing since end Feb but no results yet published.

In meantime, we can estimate from deaths.

@Imperial_JIDEA estimate 4.19% (2.8m) but only use hosp deaths.

7\\

My top-down estimate using adjusted death toll suggested 5.5m (8.8%) as of 10 Apr.

Higher concentrations in urban centres.

https://twitter.com/JamieWoodhouse/status/1248661153603084289?s=20

8\\

Without understanding true numbers infected, there's a risk we fail to tighten #Lockdown (may be needed if on plateau) or, even worse, relax lockdown too early.

Doing the former makes our current flat wave longer. Doing the latter makes it even higher.

#HerdImmunity again.

9\\

Best way, for people + economy, is:

#Lockdown hard enough

Relax (carefully) only when we're sure infected numbers v.low (sample test!) + ready

Test/trace/quar at scale to spot + stop new outbreaks before we lose control (again)

Drugs then vaccine.

10\\ END

+ Hospitalisation data also seems more positive re: trend...

https://twitter.com/jburnmurdoch/status/1250904238399598594?s=20

Of course, says little about non-hospital deaths, but hope it's still a meaningful indicator of total infections coming down.

h/t @StefanFSchubert + @jburnmurdoch

This pic sums up the risk of an early #Lockdown relaxation beautifully...

Thanks @JKFanghanel https://twitter.com/JKFanghanel/status/1252508742203117568?s=20