I found an interesting quote from a high level Qi Gong Master (Mr Li Hongzhi ) that talks about the manifestation of illness:
Ive told you that, regardless of whether its Jesus, St. Mary, Yahweh (whose ability exceeds that of even the previous two), or the Buddhas in Eastern religions, with a wave of the hand there wouldnt be one single sick person on this tiny Earth. Why arent they being compassionate and doing that for people? Because people themselves are doing bad things. Of course, this isnt to punish peopleits the principle of the universe evaluating all beings. Since humans have done bad things, they have to pay for them themselves. Suppose you killed someone, and a Buddha eliminated the karma for you.
Then, would it mean that youre allowed to kill people as you please? How could it be acceptable for a Buddha to eliminate your diseases as soon as you had killed people and generated karma? When people do bad things they have to pay for it and bear the responsibility. But when people have done bad things, the most obvious manifestation of it in the human body is sickness, which is used to punish people. Im not the only one saying thisJesus also said that people have sins. Why do people have sins? Its exactly because people have karma in their bodies. Western culture doesnt have the word karmatheres no such word in Western culture. So Jesus used the word sin to illustrate the general point. In fact, isnt having karma the same as having sins? Without sins, how could there be karma? Its the same idea.