Zanthi fever was a condition which targeted the empathic abilities of mature Betazoids. It caused the Betazoid to project their own emotions onto others but only in those individuals where a latent propensity for that emotion was present. A simple wide-spectrum anti-viral agent was enough to cure the condition.
In 2371, during a visit to Deep Space 9 during the Bajoran Gratitude Festival, Lwaxana Troi projected her feelings for Odo onto several members of the station's population. As a result, Jake Sisko developed feelings for Major Kira Nerys, Vedek Bareil lusted for Lieutenant Jadzia Dax, Dax became attracted to Commander Benjamin Sisko, Doctor Julian Bashir coupled up with Major Kira, and Quark went for Keiko O'Brien. Constable Odo seemed immune to the effects. (DS9: "Fascination")