Scrub Typhus in Kerala: Demographic, Clinical, and Laboratory Predictors of ICU Admission in a Tertiary Care Setting

Scrub typhus, a mite-borne infection caused by Orientia tsutsugamushi, is endemic in South and Southeast Asia, including India. Although increasing awareness and improved healthcare access have reduced mortality, the disease remains a significant public health concern. Kerala, a southern Indian state, has reported scrub typhus cases for decades; however, comprehensive data on its clinical profile and severity indicators are limited. This study aimed to describe the clinical characteristics of scrub typhus and identify predictors of intensive care unit (ICU) admission.

A retrospective study was conducted on scrub typhus cases diagnosed at KIMSHEALTH, Thiruvananthapuram, India, from 2015 to 2021 using electronic medical records (EMR). Scrub typhus was defined as an acute febrile disease with positive IgM ELISA. Patients with other diagnoses explaining the febrile illness or those with incomplete data were excluded. Demographic characteristics, clinical features, laboratory findings, and patient outcomes were analyzed. ICU admission was the primary outcome. Binary logistic regression was used to identify independent predictors of ICU admission.

A total of 241 patients were included in the study, of whom 74 (30.7%) required ICU admission. Most cases occurred between September and January, with a peak in December. The median age was 45 years (IQR: 24.5-60.5), and 122 (50.6%) were female. Fever lasting >7 days was present in 46.1% of patients. Common symptoms included headache (38.2%), myalgia (37.3%), vomiting (31.5%), and breathlessness (19.5%). Hepatomegaly and splenomegaly were observed in 33.2% and 28.6% of cases, respectively, while eschar was noted in 20.3%. Most patients received doxycycline (82.6%), with some receiving azithromycin (7.1%) or both (10.4%). In multivariable analysis using binary logistic regression, altered sensorium (adjusted odds ratio [aOR]: 6.63, 95% CI: 1.83-24.12, p=0.004) and breathlessness (aOR: 5.02, 95% CI: 2.31-10.90, p<0.001) were independent predictors of ICU admission.

Scrub typhus in Kerala exhibits seasonal variation, peaking from September to January. Breathlessness and altered sensorium present at admission were the strongest predictors of ICU admission The lower mortality in our study (2.1%) compared to national estimates may be attributed to improved healthcare access, early diagnosis, and prompt treatment. Further multicenter prospective studies are needed to validate these findings and improve risk stratification for severe disease.