Abstract
BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is emerging in Asian 3 countries, China, Japan and Korea, which are scrub typhus endemic areas, and its incidence is increasing. As the two infections overlap epidemiologically and clinically and the accessibility or sensitivity of diagnostic tests is limited, early clinical prediction may be useful for diagnostic and therapeutic purposes.MethodsPatients aged ≥16 years who were clinically suspected and laboratory-confirmed to be infected with Orientia tsutsugamushi or the SFTS virus in South Korea were enrolled. Clinical and laboratory parameters were compared. Scrub typhus was further subclassified according to the status of eschar and skin rash. An SFTS prediction scoring tool was generated based on a logistic regression analysis of SFTS compared with scrub typhus.ResultsThe analysis was performed on 255 patients with scrub typhus and 107 patients with SFTS. At initial presentation, subjective symptoms except for gastrointestinal symptoms, were more prominent in scrub typhus patients. In addition to the characteristic eschar and skin rash, headache was significantly more prominent in scrub typhus, while laboratory abnormalities were more prominent in SFTS. Leukopenia (white blood cell count < 4000/mm3; odds ratio [OR] 30.13), thrombocytopenia (platelet count < 80,000 /mm3; OR 19.73) and low C-reactive protein (< 1 mg/dL; OR 67.46) were consistent risk factors for SFTS (all P < 0.001). A prediction score was generated using these 3 variables, and a score ≥ 2 had a sensitivity of 93.1% (95% confidence interval [CI], 87.9–96.4%) and a specificity of 96.1% (95% CI, 93.8–97.6%) for SFTS.ConclusionThis prediction scoring tool may be useful for differentiating SFTS from eschar- or skin rash-negative scrub typhus. It is a simple and readily applicable tool with potential for use in primary care settings.
Highlights
Severe fever with thrombocytopenia syndrome (SFTS) is emerging in Asian 3 countries, China, Japan and Korea, which are scrub typhus endemic areas, and its incidence is increasing
Compared to scrub typhus patients, patients with SFTS showed a higher median age (71 years), more comorbidities such as diabetes mellitus and hypertension, a greater tendency toward infection in the summer season, a greater tendency to be infected in the eastern area of South Korea, a shorter duration from the onset of illness to the first visit, a longer duration of hospital stay, and a higher case-fatality rate (40.2% vs 0.4%, respectively) (Table 1)
In the eschar-negative scrub typhus subgroup, a score ≥ 2 had a sensitivity of 93.1% and a specificity of 93.9% for SFTS
Summary
Severe fever with thrombocytopenia syndrome (SFTS) is emerging in Asian 3 countries, China, Japan and Korea, which are scrub typhus endemic areas, and its incidence is increasing. As the two infections overlap epidemiologically and clinically and the accessibility or sensitivity of diagnostic tests is limited, early clinical prediction may be useful for diagnostic and therapeutic purposes. Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that is caused by the SFTS virus (SFTSV); it is endemic in 3 East Asian countries: China, Korea and Japan [1,2,3]. The ecological differences between vectors may characterize their epidemiological features, including the region of infection and peak epidemic seasons. There are considerable overlaps of their epidemiological and clinical features, which makes their differential diagnosis difficult, during the high epidemic season of scrub typhus. Only a high index of clinical suspicion may lead to a rapid clinical decision or an early referral, in primary care settings
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