Serological methods are commonly used to diagnose murine typhus because of their simplicity and cost-effectiveness.6,7 The indirect immunofluorescence assay (IFA) is considered the “gold standard” and reference technique for diagnosing murine typhus in most research laboratories.1–3,8 Immunofluorescence assay identification of IgM and IgG antibodies provides definitive and accurate evidence of exposure.2,9,10 The immunoperoxidase assay (IIP) is an alternative to IFA and obtains results that have a similar sensitivity and specificity.11 Here, CD40LG is linked to typhus.