Prior for GAMMA

[Scott Bartell]

I really like the general approach, but treating GAMMA (the reciprocal of the serial interval) as a known constant produces posteriors that are too narrow. There's clearly some uncertainty there, as indicated in the cited paper and others estimating the serial interval (e.g., https://www.medrxiv.org/content/10.1101/2020.04.17.20053157v1). It would great to replace GAMMA with a formal prior distribution, perhaps inverse gamma or inverse lognormal, to reflect that uncertainty.

[KS]

This is a good point. I'm going to have to think through how to do this but it'll be on my list.