CD40LG and typhus: In most clinical settings, rarely are paired acute and convalescent serum samples collected, and California Department of Public Health resolved this shortcoming through special guidelines that achieved confirmation of murine typhus serologically or by nucleic amplification in a single serum specimen of elevated IgG and IgM antibody reactive to R. typhi or other Rickettsia species by IFA or DNA amplification, respectively (CDPH 2011) [3].