What is a jungle fever couple?

Answer 1

This is a bigoted reference to an interracial relationship.

"Jungle fever" is a term that has long been used to refer to Tropical diseases, but has also been used in reference to interracial couples. It became more popularized from the 1991 Spike Lee film, Jungle Fever, starring Wesley Snipes & Annabella Sciorra. It was a controversial film since it highlighted the discomfort that interracial couples can still stir in an intolerant society. See the link below for more information about this film.

Used frequently after the movie aired, in describing someone who had developed feelings for another of a different racial/ethnic background as having "caught the jungle fever," it is also politically incorrect and offensive.

The subtext is that only a diseased white person would want to have a relationship with a black person since they are being characterized as a primitive native from the jungle. This is a prejudiced and uneducated inference.