Virus Load Kinetics in Lassa Fever Patients Treated With Ribavirin: A Retrospective Cohort Study From Southern Nigeria

The standard of care for Lassa fever is the use of ribavirin with supportive therapy. There is little information on the course of viremia and its relationship with clinical outcomes in patients treated with ribavirin. We conducted a retrospective analysis of virologic and clinical parameters of 152 reverse transcription polymerase chain reaction-confirmed Lassa fever cases admitted and treated with ribavirin therapy. We describe the Lassa virus RNA kinetics in blood in relation to the clinical course of the patients. The overall mortality was 9%. The median duration (interquartile range [IQR]) of illness before admission was 8 (5-12) days. Median (IQR) Ct values on admission ( ) were lower among patients who died (21 [20-27]) than in those who survived (34 [30-37]; < .01). The receiver operating characteristics curve of the association between outcome and Ct value at had a high classification performance, with an AUC of 0.92 (95% CI, 0.86-0.98). The median time to viral clearance (IQR) was 10 (5-15) days. The viral load decreased steadily with the duration of treatment, and all survivors achieved viral clearance within 25 days of hospitalization. Our study demonstrates that the Ct value on admission has prognostic value and Lassa fever patients treated with ribavirin typically clear the virus within 3-4 weeks of hospitalization. This kinetics has implications for the design of clinical case management and future clinical trial protocols.