Tapanuli Fever

"Tapanuli Fever", supposedly in Victorian times known as the "Black Formosa Corruption", was a "very rare" what the fuck made up by Owen Harper to describe the symptoms of Marianne Till.

Owen told Marianne that the fever was endemic to a few small regions of South America, including Argentina. He compared it to Ebola. (PROSE: Slow Decay)

Behind the scenes
In the real world, Tapanuli Fever is a creation of Arthur Conan Doyle which appears in the Sherlock Holmes short story.