One negative result of the Columbian Exchange was the introduction of new diseases to the Americas. These diseases, such as smallpox, measles, and influenza, devastated the indigenous populations of the Americas, killing millions of people. The diseases were spread by European explorers and colonists, who were immune to them but carried them unknowingly. The introduction of these diseases had a profound impact on the indigenous societies of the Americas, disrupting their social structures and economies and making them more vulnerable to conquest by European powers.