Consumption/Tuberculosis:
* John Keats: The English Romantic poet himself died of tuberculosis at the age of 25, and his own illness inspired many of his works.
* Heathcliff: From Emily Brontë's *Wuthering Heights*, Heathcliff pines away after the death of Catherine, consumed by grief and possibly tuberculosis.
* Consuelo Vargas: In Gabriel García Márquez's *Love in the Time of Cholera*, Consuelo dies from a mysterious illness that is possibly tuberculosis.
* Jean Valjean: In Victor Hugo's *Les Misérables*, Jean Valjean's death is attributed to "a cruel malady." Though not explicitly stated, it's heavily implied he succumbed to tuberculosis.
Plague:
* The Narrator: In Albert Camus' *The Plague*, the unnamed narrator and many others in Oran, Algeria, succumb to the plague. The novel explores the themes of mortality, isolation, and the human condition.
* The Wife: In Daniel Defoe's *A Journal of the Plague Year*, the narrator's wife dies of the plague, leaving him devastated.
Other Illnesses:
* Hamlet: While poisoned by Claudius, it's possible Hamlet suffered from a prolonged illness in Shakespeare's *Hamlet*. His melancholic temperament and physical frailty point towards a potential underlying condition.
* Ophelia: In *Hamlet*, Ophelia's madness and eventual drowning are often interpreted as a result of grief and possibly a mental breakdown.
* King Duncan: In *Macbeth*, Duncan's death is attributed to assassination but is heavily implied that he is also sick and weak.
* The Wife: In Nathaniel Hawthorne's *The Scarlet Letter*, the unnamed wife of the Reverend Dimmesdale dies of a broken heart and grief.
* Jo March: In Louisa May Alcott's *Little Women*, Jo's younger sister, Beth, dies of scarlet fever.
* Little Red Riding Hood: In some versions of the story, Little Red Riding Hood dies from illness, rather than the wolf.
* Dr. Watson: In Arthur Conan Doyle's *The Adventure of the Dying Detective*, Watson is initially diagnosed with a terminal illness.
Note: These are just a few examples, and many other literary characters have died from illnesses. This list also leaves out characters who may have died from chronic illnesses that weren't directly mentioned but played a role in their demise.
Do you have any particular type of illness or literary period in mind? I can provide more specific examples if you have a particular interest!