Denebian fever was a disease, presumably named for the planet Deneb V, though not restricted to that world. It was contracted primarily by individuals in poor living conditions who lacked proper nutrition. It was fatal if untreated for too long a period of time. Samir al-Halak's mother died of Denebian fever when he was ten years old. (TLE novel: Well of Souls)

Halak had claimed he and his mother lived on Vendrak IV, which may be why Anisar Batra questioned how she'd contracted Denebian fever. Although Halak did lie about this, the occurrence of Denebian fever on other worlds can be presumed to be rare but not unheard of.