A programming oversight enabled the debuff to disperse beyond the site of the Hakkar boss struggle and to wow classic gold the world at large. Hunter characters may summon and discount pets to fight in their side at will. Once ignored, all of the effects on the pets have been paused until it's known as back out again. In consequence, the pets would contract Corrupted Blood through the boss fight, disappear and then display the symptoms again elsewhere in the world map when they were again...