Yes, I would be very hesitant to get emotionally close to someone I knew beforehand to have a terminal illness or communicable disease. Would also be hesitant in the case of serious lifestyle limiting diseases such as Parkinson's.
This is going to sound harsh - but I also don't believe most disease is genetic or age related. I believe most of it is lifestyle/diet related. Even for children - who *inherit* stuff in the womb from their mother's lifestyle/diet and/or from the father's seed.