Why may malaria fever attacks fail to follow a regular pattern?

While malaria typically presents with periodic fever attacks that coincide with the synchronized release of merozoites into the bloodstream—occurring every 48 or 72 hours depending on the Plasmodium species—these patterns can be disrupted.12

Fever attacks may fail to follow a regular schedule if a patient is infected with multiple species of malaria parasites simultaneously. Additionally, the pattern may become irregular if different generations of the same parasite species are released out of synchrony. In such instances, the classic two- or three-day cycle is often replaced by more frequent occurrences of chills, fever, and sweating.1