@Bramia
Yeah, but at least he controls one human and get more of these skills. She's clearly from some human settlement and you can tell he knows her language, that's enough to go past these "regulations" you speak off. And remember, this isn't our world either so you don't even know if there are any of these regulations to follow as it could just be a very small settlement.
You said that there is no where for him to go afterwards, but at least you infected a bunch of others, gained new skills and could more easily spread the virus. He literally have nothing to lose by infecting these humans as he gains skills, more slaves, and a more understanding of this world. It's true that it's not the best way to infect humans but it's a start.
since he's a virus, he should also be slowly killing his own body so he'd need to swap bodies over and over
There is no proof of that. We don't even know if he's truly an average virus that kills the host over time. He is an intelligent virus we've never seen in our world that controls the mind within a few minutes, you shouldn't automatically assume he has the same biology as other viruses and jump to conclusions. And even if what you said is true that is even more reason to infect those humans as he'll probably need more skills and experience doing these sort of things for future reference.