High Seroprevalence of Mycoplasma pneumoniae and Chlamydia pneumoniae among Scrub Typhus Patients in South Korea

Scrub typhus is an acute febrile illness caused by the obligate intracellular organism , endemic to South Korea. The course of scrub typhus can range from a self-limiting disease to a fatal illness. Serological cross-reactivity has been reported with other intracellular organisms, including species, species, and . We conducted a retrospective study to assess the current seroprevalence of IgM and IgM in scrub typhus patients in South Korea. We enrolled 150 patients with suspected rickettsial disease over the course of 2 years. Of these patients, 60 were confirmed to have scrub typhus and had paired acute and convalescent serum. Among the 60 scrub typhus patients, 40 (66.7%) had IgM and 19 (31.7%) had IgM in acute- or convalescent phase sera. The seroconversion rates of IgG and IgM were 16.7% and 33.3%, respectively. The seroconversion rates of IgG and IgM were 8.3% and 11.7%, respectively. Compared with previous study results, this may indicate a relatively high seroprevalence of IgM and IgM in scrub typhus patients, indicating possible misdiagnosis of and infections in non-endemic scrub typhus areas.