Buddhism and terminal illness

Even in my limited knowledge on Buddhism, it makes sense to see a connection between a terminal illness (like cancer) and previous negative karma. Is there a Sutta where Buddha talks about this connection? Is it true that a terminal illness can be seen in a "positive" way, like purifying past karma? From a Buddhist prospective, are there specific ways (like rituals, prayers) for curing (or helping with) a terminal illness? Thank you all for your answers! Be well!