Malaria
Malaria is a curable condition. The parasite is resistant to some of the previously used drugs, and this resistance varies on a regional basis.
True, if untreated and depending on the strain, malaria does recur on a fairly regular (and sometimes predictable) basis, but there is no need to put up with this. If living in a malarious area, it may be that the individual is becoming re-infected. People growing up or living in malarious areas do develop a degree of immunity over time.
Malaria is a serous disease that kills more people in the world each year than any other cause.