Fanatic comes to us from the Latin word fanum, a temple. Avid devotees of a particular god would invite possession, whereby the favored god would induce a frenzy. The person would be figuratively carried away, exhibiting behavior akin to madness.
Enthusiasm, a quality displayed in fans (abbreviated from fanatic), originally meant possessed by a god. The theos (god) was ev, within.
Frantic and frenzy are two words that would suit such an occasion, and they are related. Frantic comes from a Greek form meaning affected with delirium (phrenetikos). Frenzy comes from the same basic Greek root.
Phren was a Greek word meaning mind, and it has given us phrenesis (madness), phrenetic (mentally deranged), phreniatric (relating to mental disorder), phrenitic (delirious), and others. Nowadays, frenzy is no longer seen as a gift of the gods.
SIDEBAR: NCAA report on fan behavior
(substitute @ for AT above)