While there's always room for more discussion, this topic is featured predominately in the /r/AskHistorians FAQ. It's a good place to start reading:

• I've always wondered why Native American's didn't have their own set of diseases that the European's immune systems were not prepared for. by /u/anthropology_nerd
• When Europeans brought diseases to the new world, how come Europeans themselves didn't get sick from diseases specific to the new world? by /u/anthropology_nerd
• Why weren't European settlers in North America decimated by disease like the native populations? by /u/400-Rabbits

You may also be interested in these questions that ask if most of the native population was really killed by disease from the same posters:

• What really happened in North America immediately before Columbus arrived? by /u/400-rabbits
• Were there any actions that Mesoamerican civilizations could have reasonably taken to combat the spread of smallpox? by /u/400-rabbits
• How many of the Native Americans' deaths were caused by diseases and how many by the colonial powers? by /u/Ucumu
• I am a native american living in the 1600s, someone in my village has just contracted small pox. What happens next? by /u/anthropology_nerd