The family arenaviridae consists of two antigenic groups, the New World Arenaviruses found in the Americas and Old World Arenaviruses native to Europe and Africa. These viruses chronically and asymptomatically infect rodents, which then pass the virus to humans through excretions.

In 1933, the first arenavirus to be isolated, Lymphocytic Choriomeningitis Virus, was found in samples from an encephalitis epidemic around St. Louis, Missouri. Throughout the mid-1900's, other Arenaviruses were isolated, all with similar serology, morphology, biochemical features and a natural history dependent on chronic rodent host infection. The family name is derived from Latin arenosus, meaning sandy, which alludes to the appearance caused by ribosomes in the virion.

In humans, pathologic effects can range from severe hemorrhagic fever to asymptomatic infection. New arenaviruses continue to be discovered frequently, particularly those causing outbreaks of hemorrhagic fever in the Americas.