Morbidity refers to the state of having a disease or medical condition, or to the rate at which a disease occurs in a population. A “morbidity rate” measures how many people in a given population are affected by a particular condition over a specific time period.
It’s distinct from mortality, which measures death. Morbidity is about illness; mortality is about death from illness.
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Morbidity appears in public health reporting, epidemiology, and health policy discussions. The CDC’s Morbidity and Mortality Weekly Report (MMWR) is one of the most cited public health publications. When health officials report that “morbidity from influenza increased 15% this season,” they’re describing a rise in the number of people getting sick, not necessarily dying.
In clinical contexts, “morbidity” can also refer to the undesirable aftereffects of a treatment or surgery. “Surgical morbidity” includes complications like infection, bleeding, or prolonged recovery. Lower morbidity is a key measure of treatment quality.
Morbidity vs. comorbidity
Morbidity is the presence or rate of a single disease. Comorbidity is the co-occurrence of multiple conditions in one patient. A population can have a high morbidity rate for diabetes; an individual patient can have diabetes as a comorbidity alongside heart disease.