@Jinhua: Thank you for the comment. I agree with you on the point that Priors should not be based on the general prevalence (IF you have additional information).

However, the example in the article is technically correct and is applicable to anything with rare events. I will write a follow-up article to explain how Bayes rule would be applicable in the Covid-19 context and in healthcare in general....

Scientist (several research publications in prestigious journals such as The Lancet, Brain, Thorax, IEEE Transactions), love writing for meaning & impact…