Incoherent

When rodens Ratkin succumb to their Infection, they experience a dizzying increase in their intelligence. Most absorb the local language very quickly as a result. However, a few remain linguistically challenged. The best they can muster is a repertoire of grunting noise, inchoate babbling and wheezing noises. Their crudely formed Homid mouths just can't wrap themselves around human words. If your character takes this flaw, be prepared to communicate solely like a freak who's been raised by rats.