Recrudescence is the recurrence of a disease after it is thought to be resolved. It classically appears with conditions such as malaria, in which the parasite responsible for the disease can remain present in the blood in low numbers, flaring up again in days, weeks, and sometimes months. This term is very similar to “relapse,” with some people differentiating between the two by scale; a relapse occurs after a long period of symptom-free living, while a recrudescence appears more quickly.
This return of an infection can sometimes be confused with a reinfection. In true recrudescence, the patient usually experiences an infection because the immune system has been weakened over time, allowing the infection to recur. In a reinfection, someone picks up an infectious agent again and experiences a new infection. It can sometimes be difficult to tell the difference in an area where an infection is endemic and it is easy for people to pick up new infections.
Malaria recrudescence is a very common problem, thanks to the fact that the responsible parasites are notoriously difficult to eradicate from the body entirely. Over time, they can suppress the immune system, or patients can experience immune suppression as a result of stress, fatigue, or another infection, allowing the parasites to multiply again and contribute to the development of malarial symptoms. The intensity of the recurrence can vary, depending on the patient and the situation.
When a recrudescence appears, it is treated like the primary infection, with medications being administered to address the infection, hopefully eradicate the infectious agent, and deal with symptoms which come up as a result of the infection. With conditions like malaria, the patient may also be put on a prophylactic medication regimen once the flareup resolves, with the goal of preventing a recurrence in the future. In regions where diseases like malaria are endemic, residents and visitors may also be encouraged to stay on prophylactic medication, if possible, so that they are not infected in the first place.
People may also refer to “recrudescence” in the sense of any sort of return or flaring up, even when it is not medical in nature. The word may be used in a way which is linked with unpleasant associations; in other words, the return of the circus might not be called a recrudescence because it is viewed as a fun event, while a return of militant forces to a war zone might be referred to as such because it is perceived as a negative thing.