Recrudescence
Reappearance of a disease after it has been quiescent.
A new outbreak or the return of a disease.
As, for example, the recrudescence of a pansinusitis (sinusitis, an infection involving all of the sinuses).
The original meaning of 'recrudence' was to become raw or sore again.
It came from the Latin 'crudus' (raw) via 'recrudescere' (to become raw again).
'Recrudescence' has broadened out, so there can now be the recrudescence of a rash, of arthritis, etc.