recrudescence

Recrudescence is the reappearance of disease symptoms after a period of partial or complete remission, due to resurgence of the same infection rather than a new infection. The term is used across medicine and can describe the return of clinical signs when pathogens persist in the body, re-enter the bloodstream, or reactivate latent infection when immune control wanes. Recrudescence is distinguished from relapse, where dormant forms such as hypnozoites reactivate after a long interval, and from reinfection, where symptoms arise from a new infectious agent entering the host.

In malaria, recrudescence denotes the return of parasitemia after apparent clearance, typically when drug levels fall below effective concentrations or when parasites survive in a sanctuary site; it is contrasted with relapse in P. vivax/ovale due to liver hypnozoites and with reinfection via a new bite.

Other infections may show recrudescence, including reactivation of latent herpesviruses, or resurgence of inflammatory symptoms after treatment. The term is sometimes used more broadly to describe the return of symptoms regardless of the mechanism.

Diagnosis relies on clinical history and laboratory evidence showing prior resolution followed by return of symptoms and detectable pathogen. Management focuses on addressing the underlying cause, ensuring adequate antimicrobial exposure, and preventing relapse by adherence to therapy or altering regimen as indicated. In some cases, immune suppression or drug resistance may contribute to recrudescence.

Etymology: from Latin recrudescere, to become fresh again. See also relapse and reinfection.