A Case-Control Study of the Clinical Diagnosis and Course of Lassa Fever

TLDR

The study aimed to measure the frequency and case‑fatality ratio of Lassa fever among febrile hospital admissions and to better delineate its clinical diagnosis and course. A prospective case‑control study was conducted in Sierra Leone among febrile admissions to achieve these goals. Lassa fever accounted for 10–16 % of adult admissions and 30 % of adult deaths, with a 16.5 % case‑fatality ratio; key diagnostic predictors were fever with pharyngitis, retrosternal pain, and proteinuria, while fever with sore throat and vomiting predicted mortality, and complications included mucosal bleeding, eighth‑nerve deafness, and pleural or pericardial effusions.

Abstract

A prospective case-control study of Lassa fever was established in Sierra Leone to measure the frequency and case-fatality ratio of Lassa fever among febrile hospital admissions and to better delineate the clinical diagnosis and course of this disease. Lassa fever was responsible for 10%–16% of all adult medical admissions and for rv30% of adult deaths in the two hospitals studied. The case-fatality ratio for 441 hospitalized patients was 16.5%. We found the best predictor of Lassa fever to be the combination of fever, pharyngitis, retrosternal pain, and proteinuria (predictive value together, .81); of outcome, the best predictor was the combination of fever, sore throat, and vomiting (relative risk of death, 5.5). Complications included mucosal bleeding (17%), bilateral or unilateral eighth-nerve deafness (4%), and pleural (3%) or pericardial (2%) effusion. Lassa fever is endemic in this area and is a more-common cause of hospital admission and death than has previously been described; this disease must be considered when diagnosing febrile illness in West Africa.