/Patch 4.0.1 (12-Oct-2010): Redesigned. This glyph now increases the Shadow damage portion of Scourge Strike by 30%. (Because [Festering Strike] is baseline, this glyph would be obsolete if it was not updated.)
Patch 3.2.2 (2009-09-22): Redesigned. This glyph now causes [Scourge Strike] to extend the duration of Frost Fever and Blood Plague by 3 seconds each time Scourge Strike is used on a target, up to a maximum of 9 seconds.
Previous behavior: Your Scourge Strike has a 25% chance to cause Blood Plague and Frost Fever.