The investigators propose to conduct a nationwide (Nigeria), prospective, non-interventional cohort study describing the clinical course, biological characteristics, case management and outcomes in patients hospitalized for a suspected or confirmed diagnosis of Lassa fever in tertiary medical facilities situated in the most affected Nigerian states. Special focuses will be made on situations at risk of bad outcome such as pregnancies, acute kidney injury and electrolytic imbalance in patients with confirmed Lassa fever. Participants for which the diagnosis of Lassa fever will be finally excluded by reverse-transcriptase polymerase chain reaction (RT-PCR) will constitute the control group.

The LASCOPE project refers to a nationwide, prospective, non-interventional cohort study describing the clinical course, biological characteristics, case management and outcomes in patients hospitalized for a suspected or already RT-PCR confirmed diagnosis of Lassa fever in tertiary medical facilities situated in the most affected Nigerian states. The project will start during the 2018 Lassa fever season and is intended to be extended to at least three sites throughout Nigeria on a 3 years period.

The investigators will try to depict the pathophysiological mechanisms underlying the conditions associated to a fatal outcome in patients with RT-PCR confirmed Lassa fever, with a special focus on pregnancies, acute renal injury and electrolytic imbalance.

Population and setting - Participants will be recruited in tertiary reference hospitals for Lassa fever case management in the Nigerian States identified to have the highest burden, including Owo Federal Medical Center (OFMC), Owo, Ondo State as a pilot site (list to be completed according to the outbreak dynamics).

Inclusion criteria - All the patients hospitalized for suspected or already RT-PCR confirmed Lassa fever will be eligible (no age restriction). Newborns from mothers participating in the study will also be eligible.

Sample size - Given the descriptive purpose of the study, there is no pre-determined sample size.

Follow-up - After informed consent collection, data concerning the patient's life habits, contacts, disease history, clinical and biological status, management and outcome will be collected anonymously upon admission and throughout the hospital stay. The follow-up will end 60 days after admission (60 days after delivery for pregnant women and 60 days after birth for newborns) with a phone call or a home visit (or an outpatient visit at hospital if needed).

Leftover biological samples, if any, will be stored for further analysis with the participant's agreement. The biobank will be registered once constituted and further use of stored samples will be subject to material transfer agreements.

Inclusion Criteria:

• EITHER admission (inpatient) for suspected or already RT-PCR confirmed Lassa fever OR newborn from woman infected with Lassa virus during pregnancy
• AND written informed consent of the patient or his/her legal representative (specific procedures for: immature minors, mature minors, incapable adults and unconscious adults; witnessed consent in case of illiteracy)

Exclusion Criteria:

• None

All the patients admitted in an isolation ward of one of the participating sites (tertiary hospitals) in Nigeria for a suspected or already RT-PCR confirmed diagnosis of Lassa fever during the study period are eligible to participate in LASCOPE.

The newborns from women infected by Lassa virus (RT-PCR confirmed) during their pregnancy are also eligible to participate, with the mother's agreement.

IPD underlying results in scientific publications will be made available through the deposition of a datafile in a public data repository.

Upon publication of related scientific works (undefined duration).

Free access.