Tuesday 26 May 2020

My Corona

Death, Death, Death! More Death!

I hope your immunity is up.

Governments are happily publishing loads of data on the pandemic, but not really telling you what to do with it, other than use common sense. For a recovering PhD, that can only mean one thing: spreadsheets.


This chart should update daily as more data rolls in.

While the numbers published by governments are not confusing, they are not useful. Number of deaths? Who cares! Ask Stalin.*

The death of one man is a tragedy. The death of millions is a statistic.

What I need to know is: how risky is it to go bouldering? Here's my attempt at common sense, to try and answer that.

There is some Death rate, which I guess is 1%. And there is some average time between catching the disease and dying. I guess 20 days. Why do I guess these numbers? They seem reasonable and fit with some notions like, "lockdown started in late March".

We can now work out the detection rate 20 days ago: for example: if 13 people die today, they've taken 20 days to die. 20 days ago, we measured, for example, 530 cases, however there must have been 1300 cases (1% of 1300 is 13 deaths). Out of the 1300 cases we only measured 530 cases, meaning our detection rate is 530 divided by 1300, or 40%. With more data, we can fit the detection rate and predict what it is today. That means I can guess how many people are currently out there, contagious with the disease, but do not have a positive test for it. For example, say, 71 people are found to test positive today, but detection rate is only 40%. Therefore 177 people have it. I subtract 71 from this, because if someone tests positive, it should be safe to assume they are extremely isolated (known as the Cathy Correction). So that would be 106 new cases. I add up the previous week of undetected new cases to get the total number of contagious people currently in the population. Divide by the total population and multiply by 1000, and ta-da, you have (what I'm calling) the Danger Level.

You can see the Danger Level for different populations in the graph, above. I interpret it as:

Above 5:      Do not leave the house!
Above 1:      Exercise extreme caution, go bouldering alone or not at all, avoid everyone.
Above 0.5:   Bouldering in small groups (one or two others) is ok, once or twice a week.
Any Lower? Larger groups, more regularly!

Obviously, I am no authority on the matter, in case anyone reads this (in that case, Hello! I hope you're well (if I am reading this again, Hello)). I'm aware I conveniently set these levels to fit my climbing patterns, so, blah.

Well, Maine is currently at 0.74, meaning safe for occasional bouldering. I keep a close watch on it as it's trending upward. While the assumptions are very sweeping (and wrong), the method lets me make predictions that are about 20% accurate, one week ahead - compare that to your weather app. They are the best I've come up with so far.

Scotland and UK should be commended for the heroic lockdown they have endured, and are now less dangerous than the generic USA. Maine, off the map, as always, avoided the worse of it, however Tourist season has just begun so we'll see....😬

* Quote not actually attributed to Stalin.


2 comments:

Phil said...

Why do you divide the total contagious by the population and x by 1000?

On what basis do you set Danger Levels their definitions? Otherwise something along these line which identify risk is more useful than the R number

Mike said...

Hi Phil!

The division is to compare the different countries.

On what Basis?? What do you think is more dangerous? 1000 contagious people or 2000? The more contagious people, the more danger!

For the record, I've changed to a 0.4% death rate... https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scenarios.html

The danger level had started to go negative :S