Fig 2.

Antibody responses against the indicated O. tsutsugamushi antigens were analyzed by IgG ELISA. (A) Sera from 10 scrub typhus patients (filled circles; IFA titers of ≥1:1,280) and IFA-negative sera from 10 patients with acute febrile illness (open circles) were diluted as indicated and used for ELISAs. IFA-negative sera from 10 healthy volunteers were used to determine the cutoff values (red lines; mean plus 2 standard deviations). (B) Representative IFA results for a negative serum from a patient with acute febrile illness (top) and a positive serum from a scrub typhus patient (bottom). Differential interference contrast images of O. tsutsugamushi-infected cells are shown in the left panels.