Could be. I just would have appreciated an explanation. I figured it had to do with the disease, but not everything that makes you sick also makes you rampantly attack other beings, so it was kind of coming out of nowhere. Though people seem to be constantly complaining that the Chibnall era explains things too much, so maybe those people are happy with fewer explanations. (I was post-ballet-class-exhausted when watching the episode, therefore I probably needed things spelled out for me. :-P)