Black fever, also known as visceral leishmaniasis, or kala-azar in India, had been a serious health issue in British India for a century, threatening a large part of the Indian subcontinent in the nineteenth and twentieth centuries. There were several names for it, including Dumdum fever, kala-hazar, Assam fever, black sickness, and others. The Garos described it as sarkari bemari, or ‘saheb's disease’, referring to it as a British government illness not because any Europeans had it but rather because the Garos claimed to have been unaware of it until after the sahebs (referring to the British) took over their domain. This would seem to show that following the establishment of British control, outsiders brought the disease vector to the area. In Bengal, it was referred to as kala-jwar, which means ‘black fever’ or ‘fatal fever’, while it was known in Bihar as kala-dukh, which means ‘black suffering’ or ‘fatal misery’. With a high fatality rate of more than 95 per cent, kala-azar seemed to be an uncommon but deadly disease. It began spreading so quickly in the 1870s that the British government felt compelled to attempt to control it through medical intervention, but the results of such intervention were not seen until the 1920s. From 1921 onward, kala-azar mortality significantly decreased, and modern clinical medicine significantly contributed to this reduction.

Given that the disease was one of the leading causes of death in eastern India under British control, there is no dispute about its terrible impact. Despite being a neglected illness, it has recently been mentioned extensively in the press due to its comeback to epidemic proportions in north Bihar in 1976–1977.