Hellen Keller suffered from an illness at the age of 19 months that left her deaf and blind. At the time, the cause of her illness was unknown. In The Miracle Worker, the doctor declares that Hellen has suffered from "acute congestion of the stomach and brain." A common explanation for her childhood illness is that Hellen contracted scarlet fever as a baby. More recently, however, disease specialists are theorizing that Keller suffered from bacterial meningitis, which causes a swelling of spinal cord and brain linings and can lead to deafness and blindness, unlike scarlet fever, which is not known to cause blindness. The description of a fever that appeared and disappeared suddenly also fits in with the meningitis theory. Additionally, scarlet fever was fairly common at the time and would have been easily identifiable to most physicians, particularly due to the distinct rashes it often causes. Meningitis, however, would not have displayed such observable symptoms.

If you are asking what caused Helen Keller to be both blind and deaf, the reason is that she had scarlet fever when she was two years old. This disease was fairly common when Helen was younger and the high fever it caused destroyed the nerves endings in both her eyes and ears. As a result, she could neither hear not see. The one thing that Helen's mother does remember is that before Helen became ill, she had begun to talk, something very unusual for a child her age. She would say "wa-wa" for water and that turns out to be the key for Anne Sullivan to teach her how to communicate.