Did Vikings not carry the same germs? What germs might have developed between them and columbus that had such a devastating effect on the American population?
This one gets asked a lot, and /u/Reedstilt has a good answer in the FAQ here
TLDR: Smallpox (the main disease that killed native Americans after the Colombian exchange) reached Iceland in 1241, well after the Viking colonies in North America were abandoned. Additionally, the geographic isolation of Iceland limited the number of infectious diseases that were present there for the Vikings to carry to the new world.