Whilst Epidemius is alive, keep a count of all unsaved Wounds caused by Daemons of Nurgle (friend or foe) and by spells from the Lore of Nurgle.
At the start of each of your turns, consult the Tally of Pestilence table to determine the effect of the Tally of Pestilence. Note that these effects are cumulative. If Epidemius is killed, these effects are immediately lost.