Objectives
Scrub typhus, an acute disease caused by Orientia tsutsugamushi and transmitted by larval chigger mites, is a representative autumn febrile illness in the Republic of Korea. We examined epidemiological characteristics underlying spatial heterogeneity in Busan Metropolitan City to inform region-specific prevention and control policies. Methods: We analyzed 1,645 confirmed and suspected scrub typhus cases reported in Busan from 2019 to 2023. Crude incidence rates and age-standardized incidence rates (ASIRs) per 100,000 population were calculated using the 2021 mid-year population. The chi-square test assessed associations between disease occurrence and exposure activities within the preceding 30 days. Correlation analyses examined the relationships of ASIR with environmental indicators, including per capita urban forest area, and epidemiological indicators, including prior infectious disease education. Results: The overall mean ASIR in Busan was 8.35 per 100,000 population, below the national average. However, incidence was higher in peri-urban districts, including Gijang-gun (26.12/100,000) and Gangseo-gu (15.02/100,000), than in central urban districts such as Junggu (2.20/100,000). Higher incidence was observed among women and older adults (≥60 years). ASIR correlated strongly with per capita urban forest area (r=0.92; 95% confidence interval, 0.79–0.97; p<0.001). Regional differences were significant for agriculture/forestry, gardening, and general outdoor activities (p<0.001). Districts with higher incidence also displayed higher rates of infectious disease education, although this may reflect reverse causation. Conclusion: In Busan, scrub typhus incidence was concentrated in peri-urban districts. These findings support region-specific prevention strategies, evaluation of infectious disease education, enhanced mite surveillance, and practical protective measures during fieldwork.

Objectives
This study investigated a cluster of secondary human-to-human transmission of severe fever with thrombocytopenia syndrome (SFTS) in a hospital setting, focusing on infection risk factors and the role of personal protective equipment (PPE).
Methods
A descriptive epidemiological investigation was conducted following the death of an index patient with laboratory-confirmed SFTS. A total of 27 close contacts, including healthcare workers and a funeral director, were monitored for symptoms. Suspected cases underwent real-time reverse transcription polymerase chain reaction testing. Clinical features, PPE use, and exposure histories were analyzed. The Fisher exact test was used to assess associations between PPE use and infection. Viral genotyping and sequence analyses were performed to evaluate transmission routes.
Results
The index patient deteriorated rapidly and died after repeated cardiopulmonary resuscitation (CPR), during which 8 secondary cases occurred. Most infections were identified among individuals involved in CPR or postmortem care without adequate PPE. Although not statistically significant, infection rates were higher among those who did not wear masks or who used low-filtration masks. Proper use of gloves, gowns, and goggles was associated with lower infection rates. Cycle threshold values in secondary cases (range, 34–39) were higher than in the index case (14.07), suggesting lower viral loads. Sequence analysis demonstrated 99.6%–100% homology between the index and secondary cases; all isolates were genotype B, indicating direct transmission.
Conclusion
This study provides molecular and epidemiological evidence of nosocomial SFTS transmission. Inadequate PPE use during aerosol-generating procedures likely facilitated infection, underscoring the importance of strict adherence to PPE protocols and reinforced infection control practices.