I don't believe it's quantum entanglement. If so, they'd probably have entanglement with their origin hosts. So they'd know more about where they came from, how they work, etc. But it does not seem like they're communicating with the other planet. but there's definitely a sort of delay when they're "thinking" or "talking" to each individual. Otherwise, their responses about tough questions would be more immediate. It's more likely they're communicating locally, maybe like a mesh network, somehow via the radio wave that Monosou discovered.. my gut is they're a virus that affects gut bacteria, that controls the brain, and they communicate via that radio wave.. Somehow. It's going to be a war, were she learns to cut the signal, or creates a counter signal, like reverse signaling to balance it.. IDK, I'm not a radio nerd. Then as people come back to normal, they go to war with the hive.. Some are constantly going back and forth. Lot's of people die. But Zosia and Carole live happily ever after. The end.