Hi Arim:
The body may get sick, but abiding inner silence (the witness) never does.
There is no doubt that yoga often leads to better physical health, and that a nervous system in divine flow (stillness in action) can be an aid to others. Energy flows where it is needed, where there is bhakti.
Healing has to do mainly with the faith of the one who is healing. With that, the energy for healing will come from somewhere, from everywhere.
The guru is in you.