prodrome

An early symptom indicating the onset of an attack or a disease.

A forerunner.

Any prodromal symptom.

A precursory or preliminary treatise; a prodromus (which see).

A forerunner; a precursor.

A premonitory symptom; a symptom or sensation experienced by a person which presages the onset of a disease or abnormal physiological event.

an early symptom warning of the onset of a disease

an early symptom that a disease is developing or that an attack is about to occur