According to her autobiography, The Story of My Life, Helen Keller was born with the ability to hear and to see. But when she was 19 months old, she fell suddenly ill with a condition that "closed" her eyes and ears and gave her the same sense of "unconsciousness" as a newborn baby.
At the time, the doctor diagnosed Helen with "acute congestion of the stomach and the brain." The word "congestion" is a medical term that means that Helen had an abnormal amount of blood in these organs. What caused this congestion, however, was not explained by Helen's doctors and remains a mystery even now.
Modern doctors have suggested that Helen's sudden loss of sight and hearing may have been caused by meningitis or a common childhood disease, like scarlet fever. Whatever the case, this disease left Helen as quickly as it came. Her sight and hearing, however, never returned.