A COVID-19 Risk Calculator
Shortly after I wrote last week’s blog post on COVID-19 (we tend to write the posts that don’t deal with daily news topics a bit ahead in case the day job keeps interfering), one of the better German weekly newspapers published a calculator which shows the risks of being infected with COVID-19 in various indoor model scenarios. It’s quite fascinating, and available in English.
In all scenarios, there is a group of at least 2 people, with one of them infected. Everybody follows social [1] distancing rules.
room size (both square footage and ceiling height)
time and volume of conversation
ventilation
whether and what kind of mask is worn
The article has a few pre-calculated scenarios, and you can play around with the parameters yourself.
In a restaurant, for example (18 people, 3 hrs, no ventilation, 700 sq ft / 65 m² room, loudish talking/singing, no masks – obviously), there is a 12% probability of becoming infected, with an average of 2 people infected in that 3 hour time frame. A choir rehearsal? That’s a situation which would be relevant to myself if France wasn’t currently on tighter restrictions. Assuming a fairly ideal location – it’s pretty hard to find a rehearsal room where 21 choir members can sing while keeping to physical distancing requirements [2] – and a fairly normal 2 hour rehearsal, with a cracked window you’ll have a roughly 1 in 4 risk to contract COVID. If you go with a better ventilation protocol, 10 minutes per hour, that risk drops to 1 in 8. With a ventilation system? 1 in 20. Considering a lot of the choirs I know have an average member age well above 60, that still might be too high…
The calculator has a solid scientific basis from a study by the Max Planck Institute in Mainz, Germany – an organization I tend to trust more than most as it is as uninfluenced by politics as you can get in science nowadays. And the snippets of information sprinkled throughout the article are interesting, too.
To close off today’s post, I’ll like to link another XKCD (I said I would, didn’t I?):
Seemed very topical for this blog post today in particular, and for Risklantern in general. Mark already talked about trade-offs in engineering when trying to mitigate risks, and COVID precaution fit the bill. No matter which risk, one could argue that a sufficient precaution will always feel excessive, something called a self-defeating prophecy. A prevented risk is out of sight, out of mind, and you feel like preventing risk should be a free lunch. We will have a look at cognitive biases around risk in a later post.
[1] I really detest that term, it should be called physical distancing, as that’s what it’s about. But calling it social distancing has unfortunately become the norm.
[2] Around here that means 8 m² per person, about 86 sq ft