CD40LG and Lassa fever: Therefore, serological diagnosis of acute LF cases requires a demonstration of detectable IgM or significant increase in IgG titers in paired serum samples, or necessitates confirmation by other methods, such as RT-PCR or antigen detection and IgM ELISAs.14,32,92,98–100 Clearly, there is a need for development of standardized ELISA reagents for antigen and serological testing across lineages with established performance characteristics.