Risk factors associated with severe scrub typhus in Shandong, northern China

•We conducted a case-control study to identify the risk factors associated with severe scrub typhus.•Days of duration of illness before effective antibiotic therapy, the presence of rashes, lymphadenopathy, and blood platelet counts <100×109/L were significantly associated with the severe complications of scrub typhus.•Severe scrub typhus patients were two days later to get effective treatment than scrub typhus patients without severe complications.•Improved diagnosis and timely treatment are important factors for scrub typhus patients not to get severe complications.

SummaryObjectivesThe aim of this study was to identify risk factors associated with severe scrub typhus, in order to provide a reference for clinical decision-making.MethodsA 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.ResultsThere 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 × 109/l (OR 2.226, 95% CI 1.002–4.946).ConclusionsThis 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 × 109/l, clinicians should be alert to the appearance of severe complications.