Adam Clarke on Acts 28:8

The father of Publius lay sick - Πυρετοις και δυσεντεριᾳ; Of a fever and dysentery; perhaps a cholera morbus.

Paul - prayed - That God would exert his power; and laid his hands on him, as the means which God ordinarily used to convey the energy of the Holy Spirit, and healed him; God having conveyed the healing power by this means. In such a disorder as that mentioned here by St. Luke, where the bowels were in a state of inflammation, and a general fever aiding the dysentery in its work of death, nothing less than a miracle could have made an instantaneous cure in the patient. Such a cure was wrought, and even the heathens saw that it was the hand of God.