New research has uncovered a protein enabling the replication of arenaviruses, pathogens now widespread in West Africa that are carried by rodents and can infect humans with lethal fevers. The research identified DDX3 as a key factor promoting arenavirus multiplication through its unexpected ability to promote viral RNA synthesis and dismantle normal human immune system defenses. The study may pave the way to new therapeutic treatments for arenaviruses and hemorrhagic fever.