Recrudescence

Recrudescence is the revival of material or behavior that had previously been stabilized, settled, or diminished. In medicine, it is usually defined as the recurrence of symptoms after a period of remission or quiescence,[1][2][3] in which sense it can sometimes be synonymous with relapse. In a narrower sense it can also be such a recurrence with higher severity than before the remission.[3]

In infectious diseases, recrudescence is the return of detectable symptoms in a patient whose blood stream infection has previously been at such a low level as not to be clinically demonstrable or cause symptoms. For example, the Plasmodium parasites, which are responsible for malaria, can persist in the blood without causing apparent symptoms for a few months, but recrudescence easily occurs, mainly due to challenges that tax the immune system. This is an example of where the term recrudescence is reserved for a separate meaning from relapse, as relapse in this context occurs due to activation of hypnozoites[4] in the liver.[5]

The bovine viral diarrhoea virus (bovine virus diarrhea) is said to be recrudescent for some time after clinical signs have abated, because antibodies plateau c. weeks 10–12, and are not lifelong, auto infection may potentially occur in the acutely infected non-pregnant animal.

Other diseases that may recur following a short or long period of quiescence include shingles (after chicken pox), oral herpes and genital herpes, and Brill–Zinsser disease (after epidemic typhus).