@Lustrius
Actually, I agree with the MC on that point, though not for this superficial reason.
The girl looks like she comes from a medieval setting, so it seems unreasonable at first glance that they would have advanced medical knowledge.
However...
1. It's obvious that the MC has supernatural abilities. (A sentient virus with the memories of a reincarnated human who can absorb skills from its host and review them in a game-like interface.) It's fair to assume that there
might be magic skills to treat diseases.
2. Even taking magic out of the picture, "goblins" prove that it's a different world. Culture and technology could have evolved differently from Earth. Even if weaponry looks primitive, medicine might be advanced enough to treat diseases, sentient or not.
In any case, the risk is pretty low that the people there will be too wary of a friendly wolf compared to a human (disease-wise I mean, they might still be wary of the wolf for more obvious reasons unless they are all "dumb, careless creatures"). The MC doesn't know yet if he triggers visible symptoms. And that's not necessarily something he can control: if the host body rejects the virus, that might not be something he can control as
the virus.