Argentine hemorrhagic fever (HF) is caused by the Junin virus, a member of the Arenaviridae family. Its presentation is similar to Lassa virus and the other South American viral hemorrhagic fevers such as Bolivian HF (Machupo virus), Venezuelan HF (Guanarito virus), and Brazilian HF (Sabia virus). The mortality rate is up to 30% of all symptomatic cases.

The corn mouse, Calomys musculinus, is the reservoir, and the disease is transmitted when particles from corn mouse urine or saliva are aerosolized and inhaled. In humans, the pathophysiology of the Junin virus is poorly understood. In a bioterrorist situation, the Junin virus would most likely be released as an aerosol. Russia is known to have weaponized one or more viruses that cause South American viral hemorrhagic fevers.

The incubation period is 5-14 days (usually 7-12 days). Infection is often mild or subclinical. Initial signs and symptoms may include fever, malaise, dizziness, myalgias, skin dysesthesia, oral ulcerations, lymphadenopathy, chest pain, back pain, abdominal pain, sore throat, headache, nausea, vomiting, cough, photophobia, conjunctival redness, facial flushing, and small axillary petechiae. These typically last from 7-14 days, with recovery beginning by the end of the second week of illness. Severe cases may progress to shock, pulmonary edema, diffuse mucosal hemorrhaging, and meningoencephalitis with convulsions. A vesicular and/or petechial rash on the oropharynx may be noted. Pleural effusion, ascites, and deafness are rare complications. Person-to-person transmission is possible and occurs through contact with infected body fluids and tissue. The role of airborne transmission of the Junin virus between persons is unclear. The Centers for Disease Control and Prevention (CDC) has designated Argentine HF as a Category A bioterrorism agent.