This assay is a direct ELISA detecting Human IgG and/or IgM antibody specific for LASV NP and/or Prefusion GP. Diluted samples, Calibrator, and Negative Control are incubated in microwells coated with a mixture of recombinant LASV NP and Prefusion GP antigens. Incubation allows the anti-LASV antibodies present in the samples to react with the immobilized antigen mixture. After the removal of unbound serum or plasma proteins by washing, anti-human IgG (or IgM) antibodies, labeled with horseradish peroxidase (HRP), are added forming complexes with the bound IgG (or IgM) anti-LASV antibody. Following another washing step, the bound enzyme-antibody conjugate is assayed by the addition of TMB substrate. Color develops in the wells at an intensity proportional to the concentration of IgG (or IgM) anti-LASV antibody in the sample.