Pestilence deals disease damage overtime to a target. When that target dies, if pestilence was still active, it spreads to 2 nearby enemies. Pestilence continues as long as there are nearby enemies and they are killed before its duration expires.
The above disease damage amounts (?, ?, 358-438(119-146), 418-511(139-170), 478-584(159-195)) are with STR 80 (no worn armor or items, no buffs and no AAs)