Shammy spells with disease counters?

[KelticKope]

I am aware, I am a noob, lol. I can't seem to find any literature on Disease counters, can anyone explain how these work?

The disease line of dots seem to be very mana in-efficient at lower lvls. Does stacking Disease counters perhaps help in some way?

For example I noticed

Affliction (lvl 19 shaman) increases "disease counters" by 4

while

Walking Sleep (Lvl14) Increases "disease counters" by 6 in addition to slowing the enemy.


What, if any, are the potential benefits from stacking these "disease counters"?