In June 2019, the Bolivian Ministry of Health reported a cluster of hemorrhagic fever cases that started in the municipality of Caranavi and spread to La Paz. The cause of these cases was unknown.


We obtained samples for next-generation sequencing and virus isolation. Human and rodent samples were tested using quantitative real-time reverse transcriptase-polymerase chain reaction, next-generation sequencing, and virus isolation assays.


Nine cases of hemorrhagic fever were identified; four of the patients with this disease died. The etiological agent has been identified as Mammarenavirus Chapare mammarenavirus, or Chapare virus (CHAPV), which causes Chapare hemorrhagic fever (CHHF). Likely nosocomial transmission among healthcare workers has been identified. Some patients with CHHF had neurological manifestations and those who survived had a prolonged recovery period. CHAPV RNA has been detected in a variety of human body fluids (including blood, urine, nasopharyngeal, oropharyngeal and bronchoalveolar lavage fluid, conjunctiva and semen) and in samples obtained from rats from captured small-eared pygmy rice (Oligoryzomys microtis). In CHHF survivors, viral RNA was detected up to 170 days after symptom onset; CHAPV was isolated from a semen sample obtained 86 days after symptom onset.


M. Chapare mammarenavirus has been identified as the etiological agent of CHHF. The overflow of a zoonotic reservoir and possible person-to-person transmission have been identified. This virus was detected in a species of rodent, O. microtis. (Funded by the Bolivian Ministry of Health and others.)