Kala-azar, also known as visceral leishmaniasis, is a serious infectious disease caused by the parasite Leishmania donovani. It is transmitted to humans through the bite of infected sandflies. Symptoms include prolonged fever, weight loss, anemia, and swelling of the spleen and liver. The disease primarily affects people in tropical and subtropical regions, particularly in parts of India, Bangladesh, Sudan, and Brazil. If left untreated, Kala-azar can be fatal. However, effective treatments are available, including medications like liposomal amphotericin B and miltefosine, which can help manage the disease and improve patient outcomes.