[Analysis of Laboratory Diagnostic Tests for Scrub Typhus from 2019 to 2023]

Scrub typhus is a tick-borne infectious disease caused by Orientia tsutsugamushi. When bitten by an infected tick, an eschar forms and symptoms such as fever, chills, and rash appear. This study systematically analyzed the prevalence of scrub typhus reported from 2019 to 2023 by the Korea Disease Control and Prevention Agency and 19 regional institutes of public health and the environment, examining trends according to diagnostic methods, sex, age, and region. Of the 2,607 individuals with suspected infection, 12.4% (322 patients) tested positive for scrub typhus, with 17.9% (466 patients) undergoing both polymerase chain reaction (PCR) and indirect immunofluorescence assay (IFA) tests. Among the 466 patients who were tested using both methods, Group A (positive PCR and IFA test results) demonstrated the highest positivity rate of 68.9%, suggesting a combination of past infections and reinfections. The positivity rate of the gene detection test (20.0%) was higher than that of the antibody detection test (7.8%), suggesting that PCR-based gene detection has a relatively higher sensitivity for confirming current infections. Analysis by sex and age revealed the highest positivity rate in women in their 70s (18.2%), with women consistently exhibiting higher positivity rates than men across all age groups. A regional analysis indicated that Gwangju contributed to 26.8% of patients with a positive test result, while Gangwon Province had the highest testing rate per capita (343.2%). Performing both IFA antibody detection and PCR gene detection tests simultaneously to diagnose scrub typhus is valuable for more accurately distinguishing current infections, offering critical insights to enhance the diagnostic and management strategies for scrub typhus.