Leptospirosis: Unveiling the Hidden Threat in a Non-Endemic Region of India

Leptospirosis is a globally significant yet often overlooked zoonotic disease caused by pathogenic Leptospira bacteria. The disease manifests with a wide range of non-specific symptoms, making clinical diagnosis challenging. It remains underreported especially in non-endemic settings possibly due to lack of awareness, clinical features overlapping with other common diseases and non-availability of suitable microbiological diagnostics. This study assessed the seroprevalence of leptospirosis in clinically suspected cases in a tertiary care hospital of New Delhi and it also evaluated the PCR test results obtained from urine and plasma specimens in anti-Leptospira IgM positive patients.

A retrospective observational single centre study was conducted between January 2023 and December 2024. A total of 2181 patients, clinically suspected of leptospirosis, were serologically tested using anti-Leptospira IgM ELISA kit (Panbio, Australia). Urine and whole blood specimens from sero-positive patients were further analysed using an in-house standardised PCR assay.

Among the 2181, 448 (20.6%) tested positive for anti-Leptospira IgM by ELISA. PCR testing was performed in a total of 350 out of 448 ELISA-positive patients, of which 98 (28%) patients were found to be positive either from urine/whole blood or both the specimens. A total of 140/448 (31.3%) of the seropositive cases were categorised as possible leptospirosis, while 245/448 (54.7%) were classified as presumptive leptospirosis based on modified Faine's criteria.

This study highlights a significant seropositivity rate of leptospirosis among clinically suspected cases in a tertiary care setting in New Delhi, underscoring its clinical relevance even in non-endemic regions. The combined use of serological testing and targeted PCR analysis provided complementary diagnostic value, aiding in more accurate case classification. These findings emphasise the need for heightened clinical awareness, improved diagnostic access and early detection strategies to better manage and control leptospirosis in urban healthcare settings.