Etiologies of Acute Undifferentiated Fever and Clinical Prediction of Scrub Typhus in a Non-Tropical Endemic Area

Abstract

Abstract. Scrub typhus usually presents as acute undifferentiated fever. This cross-sectional study included adult patients presenting with acute undifferentiated fever defined as any febrile illness for 14 days without evidence of localized infection. Scrub typhus cases were defined by an antibody titer of a fourfold increase in paired sera, a 1:160 in a single serum using indirect immunofluorescence assay, or a positive result of the immunochromatographic test. Multiple regression analysis identified predictors associated with scrub typhus to develop a prediction rule. Of 250 cases with known etiology of acute undifferentiated fever, influenza (28.0%), hepatitis A (25.2%), and scrub typhus (16.4%) were major causes. A prediction rule for identifying suspected cases of scrub typhus consisted of age 65 years (two points), recent fieldwork/outdoor activities (one point), onset of illness during an outbreak period (two points), myalgia (one point), and eschar (two points). The c statistic was 0.977 (95% confidence interval = 0.960-0.994). At a cutoff value 4, the sensitivity and specificity were 92.7% (79.0-98.1%) and 90.9% (86.0-94.3%), respectively. Scrub typhus, the third leading cause of acute undifferentiated fever in our region, can be identified early using the prediction rule.

Tropical fevers in Indian intensive care units: A prospective multicenter study

“…Dengue, malaria, leptospirosis, influenza A, Typhoid, rickettsiosis including scrub typhus, Japanese encephalitis (JE), and chikungunya were some of the common tropical fevers reported in patients from Asian countries. [ 2 3 4 5 6 7 ] Considerable variability exists in the proportion of these fevers in hospitalized patients as they are greatly influenced by season and geography. [ 8 ] A significant number of these patients also have one or more organ failures requiring intensive care.…”

Assessment and initial management of acute undifferentiated fever in tropical and subtropical regions

“…Scrub typhus has a characteristic skin lesion—an eschar (fig 4)—seen in 17-57% of patients as per recent reports from India,3334 and in 56-86% of patients in reports from elsewhere in Asia 333435. Examine the neck, chest, axilla, abdomen, and groin for such lesions not associated with pain, pruritus, or oedema.…”

Scrub typhus: risks, diagnostic issues, and management challenges

“… 50 , 51 Table 1 gives a summary of clinical and laboratory findings favoring or not favoring a diagnosis of scrub typhus. 23 , 25 , 28 , 52 – 58 …”

“…the authors felt that this could be used for selecting patients for empirical therapy in resource-poor situations or for performing specific laboratory tests. 23 Similarly, Siriwongpan et al devised and validated a clinical risk scoring system using a set of 526 patients with scrub typhus based on the World Health Organization (WHO) case definition. 60 – 62 …”

“… 21 – 24 This illness is thus clinically indistinguishable from malaria, dengue fever, other rickettsioses, leptospirosis, and enteric fever, which are common causes of acute undifferentiated fever in the Asia-Pacific region. 10 , 22 , 23 , 25 – 29 In this review, factors describing populations at risk, severity predictors, clinical clues, diagnostic assays, coinfections observed, and drugs available for treatment of scrub typhus are described.…”