Vengeance as a Burning Plague - Growth Option #1

I realize this is still a spirit in testing, but for any playtesters out there, I had a question re: Burning Plague's first growth option, specifically the last part:

Reclaim Cards
Gain Power Card
1 Damage per Disease at 0 Range.

Does the last part of the Growth option just take place in one land, or does it do 1 damage per Disease in *every* land where Burning Plague has Presence?
 

Like most powers, unless it says otherwise, it's a single land.