The Arenaviridae family comprises of a diverse group of single-stranded RNA viruses. There are currently 25 con-rmed members, most of which do not cause human disease. They have life cycles intimately associated with rodent reservoirs, a trait that imposes varied geographical limits on each member. Lymphocytic choriomeningitis virus (LCMV), the prototype virus, was rst described in 1934 by Armstrong and Lily. It is the most widely distributed of the Arenaviridae, being found worldwide in the house mouse (Mus musculus). The study of LCMV and its host is to a large extent responsible for our understanding of immunology and virus-host interactions.