The article discusses the history and epidemiology of leptospirosis, a severe form of jaundice caused by the Leptospira icterohaemorrhagia bacterium. Initially described by Adolf Weil in 1886, the disease was later associated with a slender coiled organism found in the blood and urine of patients. The bacterium was identified in various forms, including epidemic and sporadic cases, and has been linked to occupations such as miners, sewer workers, and those working in canals. The rat is considered the primary reservoir of infection, and the disease can be transmitted through skin abrasions, respiratory tract, or ingestion of contaminated water. Symptoms include fever, headache, jaundice, and hemorrhages, with the incubation period ranging from 4 to 12 days. The article highlights the importance of serological methods for diagnosing leptospirosis and notes that the disease is prevalent in regions like Japan, Holland, and England, with recent reports of cases in Calcutta, India. The author emphasizes the need for further research to understand the epidemiology of leptospirosis in India, where the disease appears to be widespread but lacks a common epidemiological factor.The article discusses the history and epidemiology of leptospirosis, a severe form of jaundice caused by the Leptospira icterohaemorrhagia bacterium. Initially described by Adolf Weil in 1886, the disease was later associated with a slender coiled organism found in the blood and urine of patients. The bacterium was identified in various forms, including epidemic and sporadic cases, and has been linked to occupations such as miners, sewer workers, and those working in canals. The rat is considered the primary reservoir of infection, and the disease can be transmitted through skin abrasions, respiratory tract, or ingestion of contaminated water. Symptoms include fever, headache, jaundice, and hemorrhages, with the incubation period ranging from 4 to 12 days. The article highlights the importance of serological methods for diagnosing leptospirosis and notes that the disease is prevalent in regions like Japan, Holland, and England, with recent reports of cases in Calcutta, India. The author emphasizes the need for further research to understand the epidemiology of leptospirosis in India, where the disease appears to be widespread but lacks a common epidemiological factor.