Explain how the global transfer of disease in the pre-modern world helped in the colonisation of the America

(i) Till 16th century America had been cut off from regular contact with the rest of the world.
(ii) Because of their long isolation, America’s original inhabitants had no immunity against these diseases which were brought by European conquerors. .
(iii) The diseases, once introduced, spread very fast. These killed and decimated whole communities, paving the way for conquest.