I can only think of syphilis which wasn't immediate death. Not sure this is the right place to ask this.
Hi there OP, you may be interested in this section of our FAQ on the effects of indigenous diseases on Europeans, as well as the larger FAQ section on disease in the Americas that they are part of. It's also important to note that recent scholarship has focused on disease, leading to social destabilization and violence/warfare, as one component of a larger genocide of Native American tribes. You can read more about that here:
And here: