Zanthi Fever

In the fictional Star Trek universe, Zanthi fever is a condition which targets the empathic abilities of mature Betazoids (in effect, those Betazoids of advancing years). It causes the Betazoid to project their own emotions onto others - but only in those individuals where a latent propensity for that emotion was present (for example, a Betazoid who was fearful of someone would project that emotional state, causing others in the vicinity to act upon their latent fears).

Remedies for Zanthi Fever
The nature of Zanthi Fever is not known; also, there is no information on if there is a treatment to prevent the disease. However, inoculations of simple wide-spectrum anti-viral agents to the infected Betazoid is enough to cure the condition. Individuals who are influenced by the Betazoid's projections usially return to normal within a three- to four-day period.

Recorded instances of Zanthi Fever
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. Chief Miles O'Brien and Constable Odo seemed immune to the effects.

These events transpired in the DS9 episode "Fascination".