title: Risk factors associated with severe scrub typhus in Shandong, northern China.
abstract: OBJECTIVE
  The aim of this study was to identify risk factors associated with severe scrub typhus, in order to provide a reference for clinical decision-making.
  
  
  METHODS
  A case-control study was conducted of scrub typhus patients who presented at local hospitals between 2010 and 2013. In total, 46 patients with severe scrub typhus complications (cases) and 194 without severe complications (controls) were included.
  
  
  RESULTS
  There were significant differences in the duration of illness before effective antibiotic therapy, lymphadenopathy, rash, blood platelet count, white blood cell (WBC) count, percentage neutrophils, and percentage lymphocytes between the case and control groups. Multivariate analysis demonstrated that the following four factors were significantly associated with the severe complications of scrub typhus: (1) duration of illness before effective antibiotic therapy (odds ratio (OR) 2.287, 95% confidence interval (CI) 1.096-4.770); (2) the presence of a rash (OR 3.694, 95% CI 1.300-10.495); (3) lymphadenopathy (OR 2.438, 95% CI 1.090-5.458); (4) blood platelet count <100×10(9)/l (OR 2.226, 95% CI 1.002-4.946).
  
  
  CONCLUSIONS
  This study indicates that improved diagnosis and timely treatment are important factors for the prevention of severe scrub typhus. When scrub typhus patients present with a rash, lymphadenopathy, or blood platelet count <100×10(9)/l, clinicians should be alert to the appearance of severe complications.
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, 44 Wenhuaxi Road, Jinan, Shandong 250012, China.
authors.forename: Luyan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, 44 Wenhuaxi Road, Jinan, Shandong 250012, China. Electronic address: ztzhao@sdu.edu.cn.
authors.forename: Zhongtang
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Institute for Bacterial Infectious Disease Control and Prevention, Shandong Center for Disease Control and Prevention, Jinan, China.
authors.forename: Zhenwang
authors.initials: Z
authors.lastname: Bi
authors.affiliation: Institute for Bacterial Infectious Disease Control and Prevention, Shandong Center for Disease Control and Prevention, Jinan, China.
authors.forename: Zengqiang
authors.initials: Z
authors.lastname: Kou
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, 44 Wenhuaxi Road, Jinan, Shandong 250012, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, 44 Wenhuaxi Road, Jinan, Shandong 250012, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, 44 Wenhuaxi Road, Jinan, Shandong 250012, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zheng
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002681:China; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D010976:Platelet Count; D012307:Risk Factors; D012612:Scrub Typhus / Q000175:diagnosis*
keywords: Case–control study; Orientia tsutsugamushi; Risk factor; Scrub typhus