Oh, yeah, they're here to stay... :'( Mine came from I don't know where ??? a couple of years back.
I usually see a few in the spring, the ones that overwinter. They don't bother the hives too much as long as the hive stays strong. In the fall I'll see a few more, and then dead ones over the winter on the SBB.
This early on I think that they can only survive if they stay warm enough, and if they get into the frames, the bees will abandon that and the larvae will shut down, so they can't get a toehold yet.
Once the warmer weather commences, hopefully the bees are strong enough to fight back.
I've seen quite a few in one of the hives, and a few larvae on the SBB, but not any larvae in the hive. In my observation hive, on the other hand, where it stays at least 70deg inside...there they thrived (until I cleaned the brood combs out and started over).
As it gets warmer, just keep an eye on them, don't give them any extra comb with pollen or honey that they can't defend, and if you see too many of them then start trapping.