It is not known in detail how people got infected, but it seems that Scarabs' eggs were ingested by humans with their food. The scarab grubs grew, pupate and enclose inside the body, eventually killing the host, releasing the bugs. The plague started in the city of Fahranur and wiped out almost the entire population of Istan, among them the last of the Primeval Kings. Thereafter the island was abandoned for more than 60 years, until a new human settlement was established in 720 DR. The plague also spread to other parts of Elona, but didn't have quite the devastating effect that it had in Istan.