What illness did Helen suffer from? What were the memories of illness that remain with her?

The illness that closed Helen's eyes and ears and plunged her into the unconsciousness of a new-born baby was an acute congestion of the stomach and the brain. The doctor had thought she would not live. But early one morning, the fever left as suddenly and mysteriously as it had come. There was jubilation in the family but the doctor was unsure whether her hearing and vision had been irreversibly damaged or if they could be restored.
Helen fancied that she had some confused recollections of the illness. She especially remembered the loving tenderness with which her mother tried to soothe her while she was wailing for hours due to the pain. She couldn't sleep and her eyes were dry and hot. She turned her eyes to the wall and began to recede into the dimness which would seen darken her world. Except for those fleeting memories, everything seemed unreal like a nightmare.