I ignore if there was a virgin soil epidemic and fear that even if there was we will not find any records. This for two reasons, the natives did not write anything and the Vikings stayed two to three years in their settlement, until they gave up, because of unfriendly contacts. I doubt that contacts got any closer than killing each other. There are no records about Leif's people fighting during his journey, he first landed north probably New Foundland and the journey took him furthest down, as far as today's New York. He went ashore a couple of times in different regions. It is not known yet were the later settlement was.
Leif was sent by his father Eric the Red to find fertile soil to settle, as he was banned in Scandinavia and Iceland for manslaughter. His finding, Greenland, a name he gave to attract others was not really that green as the name might have suggested.