pro·drome 
(prōdrōm′)
(prōdrōm′)n.
An early symptom indicating the onset of an attack or a disease.
[French, from Latin prodromus, precursor, from Greek prodromos, precursor : pro-, forward; see PRO-2 + dromos, running.]
pro·dromal (-drōməl), pro·dromic (-drŏmĭk) adj.