User blog comment:Octofan/Original Sin Story -Act 2- Booklet/@comment-12626831-20130910153259/@comment-12148883-20130910172615

Well, being one of the personalities of HER/IR, we can assume that the disease does come from that origin. However, the odd thing is that one of HERS symptom is to have double personalities, Irina however does not have that symptom. Also, Elluka also came from HER, but she doesn't have that disease. As such, and this is mere speculation, I believe that HER had two different diseases: Double personality and HERS. However, HERS only applied to one of her personalities: Irina's. Well, that's just my theory.