Leptospirosis is a re-emerging bacterial disease of considerable global public health concern, especially in flood-prone regions such as Northeast India. First formally described by Adolph Weil in Germany in 1886, the disease has long been endemic in tropical and subtropical regions. Recent studies have highlighted its growing presence in India’s northeastern States.
Caused by spiral-shaped bacteria from the genus Leptospira, leptospirosis is typically transmitted from animals to humans through exposure to water, soil, or food contaminated with the urine of infected animals. Each year, the disease infects over one million people and causes an estimated 60,000 deaths globally, making it one of the most significant zoonotic infections. In India, leptospirosis is endemic in several coastal and humid States, with the Andaman and Nicobar Islands – especially Port Blair – reporting the highest incidence, often exceeding 50 cases per 1,00,000 annually. However, underdiagnosis remains common due to non-specific symptoms and limited diagnostic facilities in many regions.
Zoonotic transmission lies at the core of leptospirosis. Human infection occurs through contact between contaminated water or soil and broken skin or mucous membranes, with risk peaking during floods, in rice fields, or among those working barefoot around livestock. In India, animals such as cattle, pigs, goats and dogs significantly contribute to environmental contamination. Ingestion of tainted water is a recognised but often overlooked transmission route – especially relevant in Northeast India’s rural and semi-urban areas, where human-animal interactions are close and frequent. The 2024 Goalpara outbreak, linked to contaminated water and human-animal contact, claimed 11 lives, while a fatal case in Sikkim raised alarms about the pathogen’s reach into the Eastern Himalayas.
Diagnosis has been complicated by Japanese Encephalitis (JE), which also surges during monsoons and causes deaths, as seen in Assam’s Jorhat district this July. With only 1 in 300 JE infections leading to encephalitis and JE IgM antibodies often present in healthy individuals during outbreaks, misdiagnosis is a risk. Some AES cases may be leptospirosis, especially if CSF isn’t tested for JE IgM.
Accurate differentiation is critical for effective treatment and preventing deaths. The outbreaks in Assam and Sikkim underscore a shifting epidemiological landscape. These events call for enhanced surveillance, improved diagnostics, and a ‘One Health’ approach that integrates human, animal, and environmental health. Given the region’s ecological fragility, frequent flooding, and close human-animal contact, further outbreaks are likely unless proactive measures are taken.
Despite its significant burden, leptospirosis remains neglected – not due to rarity, but due to gaps in detection and response. From the inundated streets of Port Blair to the river basins of Assam and the cloud-covered hills of Sikkim, leptospira continues to pose a silent but dangerous threat. The time has come to prioritise awareness, strengthen early detection, and invest in coordinated prevention efforts – before this overlooked killer claims more lives.