With the assessment of serologic results, however, case-patients 3, 4, and 5 might have acquired scrub typhus first and later been infected with C. burnetii; titers of IgM and IgG against O. tsutsugamushi were high, and antibodies against C. burnetii phase II antigen were negative on first tests in case-patients 4 and 5 (Appendix Table). Here, CD40LG is linked to scrub typhus.