When Europeans arrived in the Americas, they introduced diseases that devastated Native American populations. The Europeans brought smallpox, influenza, and measles, which killed many Native Americans who had no immunity. In return, Native Americans transmitted some sexually transmitted diseases to Europeans. Europeans initially enslaved Native Americans, but later turned to importing enslaved Africans who had resistance to European diseases. Both groups participated in an exchange of goods and crops, with Europeans gaining access to new world crops like potatoes, tomatoes, and tobacco in return for European livestock and grains.