To relieve of disease. Either you can pray to God or you can go to the physicians to be cured. Medicine is used to relieve diseases. God is displeased when Christians do not seek God first for their cures. We have found that demons come into a person when they have an operation and are given an anesthetic.
Demons also come into the child during birth by operation and drugs.
Other verses make a strong reference to this phenomenon. Demons can lie dormant while waiting for the right opportunity to strike. They can be in the body due to inherited sins from the ancestors. Behind a screen of bitterness, rebellion, ingratitude, and rejection hide evil spirits which work on the mind and on body chemistry and cause disturbances in physical, mental and emotional health. God has designed all the parts of the human body to work in harmony.