You consider us an advanced civilization? How generous is that.Well, a new virus, unknown to them, when they have no immunity...can rip through a population pretty quickly, Possibly before they have time to figure out what hit them. However that does not rule out the possibility that back at their home the scientist figure it out, come up with a vaccine and they return
I mean medically we're pretty advanced and look how long it took to come up with a vaccine for the corona virus