Arenaviruses are highly infectious and include viruses such as Lassa virus, Junin virus, Machupo virus. Lassa fever alone causes 100,000 to 300,000 infections per year with approximately 5,000 deaths. Strikingly, this is more than four to ten times the number of infections per year than all Ebola virus cases ever recorded (~28,000). Yet, the pace of research to develop antivirals against Arenaviruses is extremely slow. Except for Ribavirin, no FDA approved drugs or vaccines are available to treat these viruses.