Earlier tonight I speculated that Pence's unilateral conjunctivitis was a troubling sign that he might have COVID.

Is that a reasonable inference to draw? We can use Bayes' rule and a bit of Fermi estimation to figure it out.
Conjunctivitis may be a fairly rare symptom of COVID. One meta-analysis puts it at 1% of COVID cases. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7264785/

So does it really tell us anything to observe that Pence had it?

Turns out it does.
You can plug in your own numbers of course. But the bottom line is that because (1) Pence has been exposed to COVID recently, (2) unilateral conjunctivitis is rare in healthy adults and (3) it is less rare in adults with COVID, the observation substantially increases our concern.
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