It seems the infection is worsening; the plague seems to originate with corrupted grain crates (and now seems to be spread by corrupted roaches too) and those infected by the disease turn into zombies after 10 minutes of agony. These are weak creatures, but en-masse they can be deadly. This doesn't seem like an accident - it seems like a Scourge attack akin to the one that doomed poor Prince Arthas.

Thankfully, the healers of the argent dawn are on hand to deal with the plague, and our clerics and paladins stand in opposition to this vile attack