When Europeans arrived to the Americas they brought diseases the native's immune systems were not prepared for. Millions died from this. However I have not heard of diseases working on the opposite directions. Were there any diseases Europeans were not aware of that the natives carried but were immune to? Did Europeans discovered diseases in the Americas that were not found in Europe, Africa, or Asia?

Also, was European medicine advanced enough that the colonists were able to fight off most diseases the natives were host to?