Kabura SPOILER S2 EP5 Manga chapter 62(?)

2nd spoiler alert for not just S2 Ep5 and Manga chapter 62, but also for the ending of the series
(I haven’t finished the season or manga so please don’t spoil anything for me either)
(I hope I spoiled this text correctly very sorry if I didn’t)
>!After watching season 2 and reading the manga up to where it reveals Nazuna didn’t get turned by any vampire, I’ve just been wondering, what specific disease or chronic illness to kabura have, is it ever stated? (I know I’m prolly looking too far into it, just trying to kinda distract myself after someone spoiled the not so happy ending!<