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Deciding to give up his lucrative private Boston practice, Bell retained only two students, six-year-old "Georgie" Sanders, deaf from birth, and 15-year-old Mabel Hubbard. Each pupil would play an important role in the next developments. George's father, Thomas Sanders, a wealthy businessman, offered Bell a place to stay in nearby Salem with Georgie's grandmother, complete with a room to "experiment". Although the offer was made by George's mother and followed the year-long arrangement in 1872 where her son and his nurse had moved to quarters next to Bell's boarding house, it was clear that Mr. Sanders was backing the proposal. The arrangement was for teacher and student to continue their work together, with free room and board thrown in. Mabel was a bright, attractive girl who was ten years Bell's junior, but became the object of his affection. Having lost her hearing after a near-fatal bout of scarlet fever close to her fifth birthday,[N 13] she had learned to read lips but her father, Gardiner Greene Hubbard, Bell's benefactor and personal friend, wanted her to work directly with her teacher.

What disease made Mabel deaf?
scarlet fever