Arenaviruses belong to a group of rodent-borne viruses that can cause mild to severe hemorrhagic fevers.Humans mainly get infected through contact with infected rodents or their excretions,yet little is known about transmission dynamics within rodent populations.Morogoro virus (MORV) is an Old World arenavirus closely related to Lassa virus with which it shares the same host species Mastomys natalensis.We injected MORV in its host,and sampled blood and excretions at frequent intervals.Infection was acute; virus disappeared from blood after 18 days post infection (dpi) and from excretions after 39 dpi.Antibodies were present from 7 dpi and never disappeared.Some individuals experienced temporary weight loss around 10 dpi,but no other health effects were observed.Our study supports the division of arenaviruses into a chronic and an acute group,depending on whether or not infected adults clear the infection.The quantified excretion and antibody patterns can be used to inform mathematical transmission models,and are essential for understanding and controlling transmission in the natural rodent host populations.