The story is timeless, which explains why it's been adapted and retold in countless versions and multiple forms & languages, even by the author himself. Opera, ballet, film, stage, and yes, prose—all captivated by this tragic love. The movie Moulin Rouge! is one such retelling, and according to Wikipedia, there are 9 film adaptations entitled Camille, including the 1936 movie featuring Greta Garbo, not to mention the many film adaptations with other titles.
There were many challenges in trying to live up to the poignancy of the original, and of the retellings. (I'm anxious to know if I succeeded, which is to say, to see what readers think.) But one of the first was deciding how to make consumption (tuberculosis) into something relevant for modern-day Manhattan since, thankfully, TB isn't common in New York nowadays.
As I thought about the story I wanted to tell, already knowing I wanted to give more weight to the heroine's journey, I wanted to retain some of the key elements relating to consumption. The heroine's illness had to be life-threatening, and it needed to impact the lungs.
Though the versions I had seen all seemed to at least to some extent use the heroine's illness as "punishment" for an "immoral" lifestyle—meaning getting sick was something she had "deserved" due to her choices & actions—that was an element I definitely wanted to avoid. I also wanted to explore the heroine's relationship to her illness, and how long-term chronic illness, especially a condition that is expected to cause early mortality, can impact one's world view and relationships. So, the illness couldn't be acquired—and it couldn't be curable, even with the drastic difference in what medicine can achieve nowadays compared to the times of Dumas, fils.
It's actually quite interesting writing all this out and trying to explain the thought process. It makes the decision sound very deliberate—which it was—and quite painstaking—which it wasn't. All of these thoughts and considerations went through my mind in minutes, so by the time we made it from our seats at the SF Opera's performance of La Traviata to the hall of the opera house, I knew which illness my heroine would have: Cystic Fibrosis.
It helped that I already had some knowledge of the condition, though of course plenty of research was still ahead of me. And to some extent, the illness itself isn't the point—the impact of managing a difficult condition while also knowing you're going to die young is. So although Violetta's symptoms and treatments will be recognizable to anyone with knowledge of Cystic Fibrosis, the condition actually didn't end up named in the text of the story.
Still, having a genetic condition that had to be managed since early childhood impacted Violetta on a deep level, something that is rarely if ever explored in stories featuring severely ill characters. Most often, these characters are flattened into inspirational archetypes—the means through which the real main characters learn some lesson, have their world view and life trajectory shifted as a result of knowing the character dealing with illness. And I'm not just talking about retellings of this story. Consider A Walk to Remember, Here On Earth, My Sister's Keeper (the movie version—from what I've read the book version has a drastically different ending); Henry from Grey's Anatomy; I'd say Beth from Little Women counts; and even arguably Dory from Finding Nemo. Sometimes of course chronically ill characters are flattened into the opposite archetype—of the bitter ill person—but still their story tends to revolve around being a tool that transforms the life of the "normal" character(s), such as in Me Before You or You're Not You.
I can only hope that in Fallen I succeeded in conveying the complexity of Violetta to readers, regardless of their familiarity with CF. But for those interested in learning more, a good place to start is the Cystic Fibrosis Foundation's website.
And of course, don't forget to grab your copy of Fallen, which is—4 years and 4 months to the day after I first started writing it—finally available!