In his life of Saint Catherine of Siena, her confessor, Saint Raymond of Capua, narrates that after her arrival in Pisa she became the guest of a certain Gherardo de' Buonconti. One day her host brought to her attention a young man of about twenty years of age, for whose good health he implored her prayers. The Saint was told that the young man had been beset by daily attacks of fever for eighteen months.
Though he was not at the moment suffering these attacks, the previous and continuous onslaughts had changed him completely from a healthy young man into a feeble creature for whom no medical care had been of any help. His feeble state was plain to see in his pale and emaciated face.
Saint Catherine's heart was moved with compassion for the poor youth, but she began by asking him how long it had been since he had rid himself of his sins through sacramental confession. When he replied that it had been several years, she immediately said: "There you have the reason why the Lord willed you to undergo this chastisement. You have allowed altogether too long a time go by without cleansing your soul by holy confession. Go at once to confession, my son, and vomit up the corruption of sin that has infected your soul and body." The Saint then sent for Father Thomas, her first confessor, and handed the sick man over to him for confession and absolution of sins.
When this had been done and the sick man had come back to her, she laid her hand on one of his shoulders and said: "Go now, son, with the peace of Jesus Christ Our Lord; it is my will that you should be troubled by those fevers no more." As she spoke, it was done: From that moment the young man never again suffered the fever, nor any symptom of it.
From The Life of Catherine of Siena
By Saint Raymond of Capua