A neglected tropical disease, kala azar is caused by a parasite, spread to humans through the bite of infected female sand flies. It attacks the immune system and is almost always fatal if not treated.

Also known as visceral leishmaniasis, kala azar is the most serious form of leishmaniasis and is endemic in 76 countries, with hundreds of millions at risk of infection. There are between 50,000 and 90,000 new cases a year, about 90 per cent of which occur in Brazil, Ethiopia, India, Kenya, Somalia, South Sudan and Sudan. Between 1989 and 2020, MSF teams treated nearly 150,000 people for kala azar; over a third in South Sudan.

Diagnosis and treatment of the disease, especially of the variety found in eastern Africa, can be complex and painful.