I think the Fireflies infect some monkeys to see how it affects them, but I think all that happens is that they can transmit the disease through bodily fluids. Then again, because of how recent it was, we don't know what they'd look like after a few years. Maybe we'd have clicker-monkeys, and we'd all be screwed, "Dawn of the Planet of the Apes: But They're Zombies" style. Basically "28 Days Later", I guess. Thanks again for reading and commenting!