During the Heroic Professor Putricide fight in Icecrown Citadel, if you receive Unbound Plague, you will begin a 10 second countdown in /yell. The countdown looks like this:
Help me in 10 seconds!
Help me in 9 seconds!
Help me NOW!
Plagued is about 100 lines of code. It uses 8K of memory and zero CPU until you have actually pulled Putricide.
Installing AddonLoader will cause this add-on to only load when you enter the appropriate raid zone or sub-zone.