typhus fever vs rickettsiosis

typhus fever and rickettsiosis both are nouns.

Word	Noun	Adjective	Verb	Adverb
typhus fever	Yes	No	No	No
rickettsiosis	Yes	No	No	No

As nouns, rickettsiosis is a hypernym of typhus fever; that is, rickettsiosis is a word with a broader meaning than typhus fever:

typhus fever: rickettsial disease transmitted by body lice and characterized by skin rash and high fever
rickettsiosis: infectious disease caused by ticks or mites or body lice infected with rickettsial bacteria

Other hypernyms of typhus fever include rickettsial disease.

typhus fever (noun)	rickettsiosis (noun)
rickettsial disease transmitted by body lice and characterized by skin rash and high fever	infectious disease caused by ticks or mites or body lice infected with rickettsial bacteria