Best treatment in 17th century? Prayer

[O]n Henry's second Sabbath, the infant appeared to slip away. Samuel knew from experience that his best option now was prayer. A seventeenth-century doctor could do little or nothing for a seriously ill newborn. Boston had few physicians, and those few men who had come from England with university degrees in "Physic"—the study of the ancient writings of Hippocrates, Aristotle, and Galen—could offer no effective treatments for most illnesses the Sewalls faced: smallpox, influenza, other viruses, and dysentery. Prevailing treatments included bleedings, purgings, the ingestion of concoctions of lavender and other herbs or oil of amber, and for a sore throat the application of the inside of a crushed swallow's nest. The medical profession in its modern sense did not exist.

Samuel was desperate. He wrote notes to the Reverends Samuel Willard and Joshua Moody . . . asking for public and private prayers. A servant raced to deliver the notes. 

Eve LaPlante, Salem Witch Judge: The Life and Repentance of Samuel Sewall (New York: HarperCollins e-books: 2007), p.  17