relapse

To return to a former state.

To become sicker after partial recovery from an illness.

To recur. Used of an illness.

To slip back into bad ways; backslide.

A return to a former state, especially after apparent improvement.

To slip or slide back; return.

To fall back; return to a former bad state or practice; backslide: as, to relapse into vice or error after amendment.

To fall back from recovery or a convalescent state.

A sliding or falling back, particularly into a former evil state.