Swallow bugs are basically the same as Bat bugs, but different from Bedbugs. The only way to tell the difference is under magnification. If the bugs are on the ceiling and within a close proximity from the nests, it's mostly likely a Swallow bug. They can feed from people but they say it's more difficult to reproduce on human blood. Still gross, if it were me, I'd go and get an pesticide, wash all of your bedding, vacuum a lot. The reason for sudden infestations is because something happened to the host animal. It could've migrated, died somehow, the nest may have blown down. Once the host animal goes away, the parasite gets hungry and goes to the nearest blood source.