Orkett's disease

Orkett's disease was caused by a virus that affected thousands of Bajoran children during the Cardassian Occupation of Bajor. The disease was usually terminal unless a suitable bone marrow transplant was performed. 

In 2371, USS Voyager's EMH discovered that Seska's blood chemistry was not consistent with that of a Bajoran. Her cover story was that she suffered from Orkett's disease as a child during the Occupation of Bajor, and that she had received a bone marrow transplant from a Cardassian woman named Kattell, although the Doctor had considered and dismissed that explanation before she even brought it up as the sheer scale of Cardassian bone marrow in her system meant that she could only be a Cardassian. 

External link
Orkett'sche Krankheit Enfermedad de Orkett