In 1882, Helen Keller suffered from an illness her doctor called a brain fever and lost her ability to see, speak and hear. In the 21st century, the exact illness remains a mystery, but some doctors believe she suffered from either scarlet fever or meningitis.
At 18 months of age, Helen Keller developed an illness that caused her body temperature to rise to dangerous levels. Within a couple days of her recovery, Helen's mother noticed a change in her daughter's reaction or lack of reaction to things like the ringing of the dinner bell and waving a hand in front of the child's face.
Helen Keller was developmentally on schedule until this brain fever struck. She began talking when she was around 6 months old and walking her first birthday. The brain fever was responsible for her loss of speech, sight and hearing.
At age 7, Helen Keller met Anne Sullivan who taught her sign language by writing on her hand and forcing the young child to feel the associated item. For instance, Sullivan would spell out “water” and then put Helen's hand under running water from the water pump. It took more than 25 years for Helen Keller to regain the ability to speak.