A case series of possibly recrudescent Orientia tsutsugamushi infection presenting as pneumonia.

Orientia tsutsugamushi remains latent in humans after scrub typhus. Pneumonia occurs as a complication of scrub typhus in the late-phase disease. However, pneumonia may also occur as a presenting manifestation of O. tsutsugamushi infection. We reviewed the cases of 3 patients with atypical pneumonia who presented at our hospital and were later confirmed to have O. tsutsugamushi infection by serology, nested polymerase chain reaction (PCR), and cell culture. All patients were young adults with no history of scrub typhus, and none claimed to have recently been exposed to areas where scrub typhus is endemic. Two cases occurred in non-outbreak seasons. Furthermore, eschar was not observed. Pneumonia was documented within 4 days after fever onset. The immunoglobulin (Ig) G antibody titers against O. tsutsugamushi were higher than the IgM titers, although the serologic test results were less helpful in the diagnosis. Nested PCR and cell culture of blood specimens confirmed the diagnosis of O. tsutsugamushi infection. These findings suggest that pneumonia can occur as a result of recrudescence of latent O. tsutsugamushi infection.