ADF syndrome was a bacteriophage which the afflicted Eeiauons called "the long death". The first stage of the disease involves pained slow movements. The second stage leaves the patient hunched over with pain, leading to the final catatonic stage.
When the disease starting to cross over to others, the Wilson-Chapel serum, was only used as a stop gap, till the cure was found.
A much lighter version of this disease experienced by Sivaoans was called Noisy-Baby. (TOS novel: Uhura's Song) Jinx to-Ennien knew of Thunderstroke cure and used to save Pavel Chekov during the walk.