Re-emergence of Scrub Typhus in India: A Systematic Review and Meta-Analysis of Prevalence and Fatality

Scrub typhus, caused by Orientia tsutsugamushi , is re-emerging as a cause of acute febrile illness (AFI) in India. Its nonspecific presentation and diagnostic challenges contribute to underdiagnosis and preventable mortality. To estimate the pooled prevalence of scrub typhus among AFI cases in India and to summarize the pooled case fatality rate (CFR).

A systematic search of PubMed and Google Scholar was conducted for literature published between January 2013 and October 2023 (last search: September 15, 2023). Full search strings and filters are provided. Observational studies from India reporting laboratory-confirmed scrub typhus among patients with AFI were included. Community serosurveys were analyzed separately from hospital-based AFI cohorts. Studies using only Weil-Felix test were excluded from the main analysis; a sensitivity analysis including them is presented. Two reviewers independently extracted data. A random-effects meta-analysis model was used. Due to extreme heterogeneity (I 2 > 90%), pooled estimates are presented with caution, and medians and ranges are also reported.

From 36 studies (excluding pre-2013 and Weil-Felix-only studies from main analysis), the pooled prevalence of scrub typhus among AFI cases was 26.4% (95% CI: 22.0-31.0%; I 2 = 94%; median: 24.5%, range: 8-53%). The pooled CFR among confirmed cases was 7.7% (95% CI: 4.4-11.7%; I 2 = 89%; median: 6.5%, range: 2-23%). The classic eschar was present in only 29% (95% CI: 22-37%) of patients. Community serosurveys (n=7) showed substantially lower prevalence (pooled 8.2%, 95% CI: 4.1-13.5%). Heterogeneity was high.

Available hospital-based studies consistently identify scrub typhus as an important cause of acute febrile illness in several regions of India, although the magnitude of burden varies substantially between settings. The low frequency of eschar and diagnostic variability underscore the need for heightened clinical suspicion and standardized testing. Given the very high heterogeneity, pooled estimates should be interpreted cautiously, and readers are encouraged to examine the range and median values presented.