Do you think we could interact with them in a beneficial way without bringing disease or drastically changing their way of life?

Ethics and moralities of actually doing so aside for two moments...

1) I'm trying to imagine a sterilized delivery system of treatments that such tribes would be able to understand enough to use.

2) Similar to "how do we communicate to the deep future not to enter nuclear waste storage facilities", how do we communicate to such people when not only is there a language barrier but also a gap of hundreds [thousands?] of technological &c progress as well.

Giving them gifts from the gods (i.e. packages without contact) would only make them reliant on us and could have unknown effects on their culture, increasing (if they have it) human sacrifice in times of illness, for example.