title: Urbanization of scrub typhus disease in South Korea.
abstract: BACKGROUND
  Scrub typhus is an endemic disease in Asia. It has been a rural disease, but indigenous urban cases have been observed in Seoul, South Korea. Urban scrub typhus may have a significant impact because of the large population.
  
  
  METHODS
  Indigenous urban scrub typhus was epidemiologically identified in Seoul, the largest metropolitan city in South Korea, using national notifiable disease data from 2010 to 2013. For detailed analysis of clinical features, patients from one hospital that reported the majority of cases were selected and compared to a historic control group. Chigger mites were prospectively collected in the city using a direct chigger mite-collecting trap, and identified using both phenotypic and 18S rDNA sequencing analyses. Their infection with Orientia tsutsugamushi was confirmed by sequencing the 56-kDa antigen gene.
  
  
  RESULTS
  Eighty-eight cases of urban scrub typhus were determined in Seoul. The possible sites of infection were mountainous areas (56.8%), city parks (20.5%), the vicinity of one's own residence (17.0%), and riversides (5.7%). Eighty-seven chigger mites were collected in Gwanak mountain, one of the suspected infection sites in southern Seoul, and seventy-six (87.4%) of them were identified as Helenicula miyagawai and eight (9.2%) as Leptotrombidium scutellare. Pooled DNA extracted from H. miyagawai mites yielded O. tsutsugamushi Boryong strain. Twenty-six patients from one hospital showed low APACHE II score (3.4 ± 2.7), low complication rate (3.8%), and no hypokalemia.
  
  
  CONCLUSIONS
  We identified the presence of indigenous urban scrub typhus in Seoul, and a subgroup of them had mild clinical features. The chigger mite H. miyagawai infected with O. tsutsugamushi within the city was found. In endemic area, urban scrub typhus needs to be considered as one of the differential febrile diseases and a target for prevention.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Internal Medicine, Boramae Medical Center, Seoul, Republic of Korea.
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Park
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine and Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Na-Young
authors.initials: NY
authors.lastname: Ha
authors.affiliation: Medical Research Center, Seoul National University College of Medicine, Seoul, Republic of Korea; Seoul Center for Infectious Disease Control, Seoul, Republic of Korea.
authors.forename: Boyeong
authors.initials: B
authors.lastname: Ryu
authors.affiliation: Department of Internal Medicine, Boramae Medical Center, Seoul, Republic of Korea; Seoul Center for Infectious Disease Control, Seoul, Republic of Korea.
authors.forename: Ji Hwan
authors.initials: JH
authors.lastname: Bang
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine and Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Hoyeon
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine and Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine and Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Gwanghun
authors.initials: G
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea; Seoul Center for Infectious Disease Control, Seoul, Republic of Korea.
authors.forename: Myoung-don
authors.initials: MD
authors.lastname: Oh
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine and Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Nam-Hyuk
authors.initials: NH
authors.lastname: Cho
authors.affiliation: Seoul Center for Infectious Disease Control, Seoul, Republic of Korea; Department of Family Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Jong-koo
authors.initials: JK
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001096:Arachnid Vectors / Q000382:microbiology*; D003710:Demography; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012285:Orientia tsutsugamushi / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D011446:Prospective Studies; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D012612:Scrub Typhus / Q000453:epidemiology* / Q000382:microbiology; D011795:Surveys and Questionnaires; D014324:Trombiculidae / Q000382:microbiology*; D014505:Urban Population; D014507:Urbanization
chemical_list: D000907:Antibodies, Bacterial