Scanning the entire region, it doesn't actually seem to originate at the river; in fact, it seems to<em>end</em>at the river's border, mostly because it's wide and fast running, making it difficult to cross, though he does find evidence of the sickness on the far side of the river, as well. Not as prominently, but still present.<br/><br/>Tracing it back, it seems to come from further south, and seems to mostly originate in a series of small villages, along the southern edge of the elven lands, near a mostly uninhabited area, though it's clear it was inhabited at one point, as ancient ruins dot the landscape.