Tuesday, 7 April 2020

Coronavirus: eight European countries are now “over the hump!”

I’ve been doing some more playing with the new-cases figures for coronavirus. I took the raw figures since March 17th from worldometers.info for the following countries: Spain, Italy, Germany, UK, Switzerland, Belgium, Netherlands, Austria, Portugal, Sweden, Norway, Ireland, Denmark. I left out France, because of their recent data issues. I used Excel to smooth the figures over 7-day periods (so e.g. for March 20th I averaged the figures from March 17th to 23rd inclusive). I chose 7 days, because that is roughly the period of the “wobble” I saw in many countries’ data when I first looked into the detail a few days ago.

I came up with some interesting results. The countries divided clearly into three groups:

(1)   Eight in which the smoothed new cases have already peaked and are on a downward trend: Spain, Italy, Germany, Switzerland, Belgium, Austria, Portugal, Norway.

(2)   One (Netherlands) where smoothed new cases have only very recently peaked, and it’s not clear whether or not that will be the final peak.

(3)   Four in which the smoothed new cases have not yet peaked: UK, Sweden, Ireland, Denmark.

For the first two groups, I worked out by how many per cent per day the numbers have been falling since the peak. I took the latest smoothed number of cases (dated 3rd April, because that’s the last day for which I have a full 3 days of following data), divided by the peak number of cases, then took the Nth root, where N is the number of days between the peak and 3rd April, and converted the result to a percentage decay per day. My Excel formula was:

=ROUND((1-EXP(LN(<latest count>/< count at peak>)/<number of days since peak>))*100,2)

Obviously, the Netherlands was an outlier on the low side. Of the remainder, six all showed a decay rate between 1.8% and 2.8% per day: Germany 2.79%, Switzerland 2.52%, Spain and Italy both 2.25%, Belgium 2.03%, Portugal 1.8%. If I take the Spanish and Italian figure as representative, that corresponds to a half-life of 30 days for new cases of the virus.

But in some places, it’s better than we thought. Norway is showing a decay rate of 3.55% per day, and Austria a whopping 7.25% per day. Indeed, the smoothed new Austrian cases per day are already down very nearly to half of what they were at their peak on 25th March.

Whatever the Austrians have been doing to combat this virus, seems to be working. They did quarantine one particular town which was a big source of infection, which as far as I know no-one else has done. And apparently, they have mandated that face-masks are worn in stores; but that only started yesterday, so can’t have had any effect on these figures. So why, I wonder, has the Austrian experience been so much less bad than anyone else’s? Inquiring minds want to know, and to apply that knowledge.

Indeed, the Austrians, and the Danes too, have very recently announced that the restrictions are to be relaxed over the next few weeks. For Europeans it looks as if, as Winston Churchill famously said after the battle of El Alamein: “Now this is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.”

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