We don't know what they have in the code. They could have "viruses" that don't actually affect gameplay at all, but spreads like a virus would.
You're uninformed, it was a debuff that, through a game bug, was able to spread beyond it's dungeon into the outside world. It discontented higher level players but it's high DPS demolished starting characters. It spread to those in close vicinity of the people who had the debuff.
It was totally unintentional and Blizzard admitted they made a big mistake in letting it occur.
