Clinical and Environmental Investigation of a Scrub Typhus Case in Delhi NCR: Implications for Public Health

Abstract

Introduction: Scrub typhus, caused by Orientia tsutsugamushi, is a re-emerging zoonotic infection in India, transmitted by larval mites (chiggers), and is an important cause of undifferentiated febrile illness. Early diagnosis is often missed due to nonspecific symptoms, leading to life-threatening complications. While scrub typhus has been historically reported from rural and hilly regions of India, recent studies indicate the emergence of urban and peri-urban hotspots, including Delhi and the adjoining regions. Aim: To describe a field investigation of a confirmed scrub typhus case in Delhi-NCR, detailing clinical, epidemiological, and environmental aspects, and to highlight implications for urban public health surveillance. Case Presentation: We investigated a 22-year-old male admitted with a 10-day history of fever, weakness, and a characteristic necrotic eschar over the left flank. Scrub typhus IgM ELISA was positive, confirming the diagnosis. The patient had no recent travel history but reported the presence of rodent burrows and bed bug infestation around his residence, indicating potential exposure to chigger habitats in the domestic environment. He was successfully treated with intravenous doxycycline along with supportive therapy. Field Investigation: An environmental surveillance was conducted in the area of residence, where soil samples were taken. Two out of ten soil samples (20%) came out to be positive. Inspection revealed poor living hygiene, vegetation in peri-domestic area and evidence of rodent activity, providing potential foci for mite breeding. Results: The patient presented with a febrile illness and a classical eschar. Laboratory confirmation by IgM ELISA established scrub typhus diagnosis. Two out of ten (20%) of soil samples collected from the living quarters tested positive for O. tsutsugamushi on PCR, confirming the presence of environmental reservoirs. Rodent burrows and bedding infestation were evident, indicating peri-domestic transmission risk. Conclusion: Scrub typhus can occur in urban areas; timely diagnosis, entomological surveillance, and preventive measures are essential. Even a single case in Delhi should trigger an outbreak investigation due to emerging hot spots in Delhi and the National Capital Region (NCR).