That is the result of activation, not the cause. Is it some sort of plot-triggered event for the plague as a whole? Is it triggered by dropping an ability score of the host to 0? What?
Running: Ruceeglaelsktinag ICOOCMap
My Dream Campaign: ICOOC No Map Right Now.
For everything else (including my extensive homebrew) see: Extended Signature My Homebrew is meant to be used, but, if you do, PLEASE tell me how it goes.