Thread by @jnordvig

There is a big debate about the European 2nd wave, and whether it is serious or not. And it is surely hard to look at cases alone, since the testing quantity is totally different. I think looking at the dynamic CFRs is very informative....

= mini-THREAD

The table here shows Case Fatality Rates over time for several European countries, using recent deaths vs lagged cases.

It shows that you cannot really talk about severity in a uniform sense.

Some countries, such as France, Finland, Sweden, Norway an Denmark have stable an very low fatality rates (<1%) even with cases ticking up.

But other countries, especially Poland, Hungary, Czech Republic and recently also Greece and Italy and to some degree the UK have CFRs moving higher to 2-7%, suggesting that they have a large un-recorded outbreak.

The undetected outbreak issues is also clear from hit ratios/positivity rates. See for example how testing is lagging in Italy:

And positivity is also spiking in Poland (outside our normal grid, so using OWID as source)

[positivity is signalled via color of line]

The rising CFRs (which signal a big undetected outbreak in certain countries) is part of the the reason why our fatality forecast is now sharply accelerating, and putting daily fatalities >1000 within a few weeks (although Poland is outside this group).

https://twitter.com/ExanteData/status/1319398891083747329

All told, the European second wave has come very quickly, an since CFRs are moving higher in a number of countries, it is hard to argue that it is not a deadly wave (although not as deadly as the 1st).

I will leave it at that. We worry that the 2nd wave is potent due to weather effects & that the measures that were sufficient in the warmer weather to control Rt will not cut it now. In any case, deaths will continue to rise in coming weeks (CFRs show that). That is a given. END