Currently a lot of discussions around #COVID19 superspreading events, so it's time for a thread to add some context and reply to common comments about this...
1/n
1/n
https://twitter.com/gijn/status/1320909339033509889
"*random setting* is not in the database! So it must safe!"
That's a risky conclusion to make. Not detecting transmission ≠ transmission didn't happen! There are a lot of biases that make it hard to identify some settings. We also have to remember that...
2/n
That's a risky conclusion to make. Not detecting transmission ≠ transmission didn't happen! There are a lot of biases that make it hard to identify some settings. We also have to remember that...
2/n
... many setting have been closed / reduced visitors these past few months. Hard for transmission to happen in a setting when no-one's there! And, just based on that, risky to assume there won't be any transmission when people come back.
3/n
3/n
"Okay, but *setting 1* has more cases than *setting 2*! So surely *setting 1* is more dangerous!"
Ranking settings of transmission is tempting, but misleading in reality.
4/n
Ranking settings of transmission is tempting, but misleading in reality.
4/n
Ranking two settings would imply that we are really confident we've detected all the transmission events in both settings. But perhaps it's just because it's easier to detect transmission in setting 1 than setting 2, so we found more there!
5/n
5/n
We would also have to weigh transmission by the relative attendance in each setting. If more people are visiting setting 1 then, all other things equal, we would expect more transmission there than in setting 2.
6/n
6/n
"If we can't even say which settings are high risk, then what's the point of this database? "
It's useful to look at the characteristics of settings identified. What do the settings where transmission occurred have in common?
7/n
It's useful to look at the characteristics of settings identified. What do the settings where transmission occurred have in common?
7/n
The majority of settings of transmission are indoors, where people are in close proximity for a long time, with poor ventilation & cold air. These are the factors that facilitate spread, and the targets for interventions to reduce risk in all settings.
8/n
8/n
In summary, there are many easily-forgotten limitations that make it hard to rank settings of #COVID19 transmission by risk. Instead, we should think about the shared characteristics of places where transmission happened, and use these to design interventions to reduce risk.
9/9
9/9
• • •
Missing some Tweet in this thread? You can try to
force a refresh
