Kala azar-HIV co-infection is an emerging public health problem in Bihar, India. Kala azar, a neglected tropical disease spread through the bite of a sandfly, thrives in agricultural settings and is prevalent in Bihar. It's almost always fatal if left untreated. People living with HIV are far more likely to develop kala azar in places where it's endemic, creating an even more deadly combination. Since 2015, MSF has treated over 700 cases of HIV-kala azar co-infection.