Burden of scrub typhus in north-eastern region of India: A systematic review and meta-regression analysis

Background and objectives Scrub typhus is endemic in India and neighbouring countries. India's north-eastern region (NER) is geographically and ecologically distinct from the rest of the country, with variations in climate, ecology, land use patterns, and population behaviours, heightening the risk of scrub typhus among the residents. Scrub typhus remains an under-explored zoonotic disease in the region. Methods A systematic review was conducted to estimate the burden of scrub typhus in the NER of India. Six databases were searched for studies on the prevalence, seroprevalence, and case fatality rate of scrub typhus in NER. A meta-regression analysis was conducted to ascertain the sources of heterogeneity. Results A total of 718 studies were retrieved from the included databases. Twelve hospital-based prevalence studies spanning 7 States and 4 community-based seroprevalence studies spanning 5 States met the eligibility criteria. The prevalence of scrub typhus among patients with febrile illness and/or clinically suspected cases ranged from 7-36%, while seroprevalence among healthy individuals ranged from 0.8-45%; the case fatality rate ranged from 3-13%. Multivariable meta-regression identified region (P=0.004) and sample size (P=0.003) as significant moderators for prevalence, but not for seroprevalence. Interpretation and conclusions This review highlights the under-recognised burden of scrub typhus in the NER of India. Studies, though limited, underscore the need for better epidemiological data, enhanced surveillance, and community-based research, particularly in high-risk areas.