If I'm not mistaken, Erick the Red sailed into the area around Newfoundland around 1000 CE. Assuming he had contact with native peoples living there, why did Old World diseases not run rampant in the New World then as they did 500 years later when Columbus and the conquistadores sailed to South America/Carribean? Were the colder parts of North America not immediately ammenable to Old World diseases, or was trade and connection between tribes lesser in the North?