Mostly refers to interracial attraction because of stereotypes or curiosity. In Spike Lee's film (the origin of the term's popularity) both characters are referred to as suffering the 'disease' and are criticized by members of their race for the relationship.
<i>I've</i> Got jungle fever
She's got jungle fever
<i>We've</i> got jungle fever
A Stevie Wonder song about black man/white woman love.
He's gone white girl hazy
They got jungle fever"--Stevie Wonder.
Not all Black-White relationships are based on Jungle Fever. However, one may be able to identify relationships that are based on Jungle Fever by analyzing the couple's dating history. For instance, if a White person who lives in an area with few Blacks has only dated Blacks, then it's likely that that person has Jungle Fever.
Generally considered a derogatory term that hints at past colonial relationships between Blacks and Whites, where White colonizers enter, with fascination, the African Jungle in order to learn from and conquer it.