Plague transmission rate (2nd hand)

[Wiply]

Trying to figure out the 2nd hand transmission rate for plague, i.e. if you hit a non-unead with plague, whats the chance that you get it?

I've looked in the guide and searched around for it, but it doesnt seem to be stated anywhere.

First hand contraction seems to be 20%, but 2nd hand is supposedly alot less (from experience), does anyone know what it is?

[Bishop]

I don't think i've ever seen people tracking it, haven't a clue myself.