In the dusty courtyard of a crowded clinic in Old Fangak, in South Sudan’s Jonglei state, throngs of people, some of them under mosquito nets strung between trees, wait to get tested for kala-azar, amid the worst continuous outbreak in three decades. Last year, this clinic – which lacks electricity or running water - handled around half the 11,000 total recorded cases of the parasitical disease, also known as visceral leishmaniasis. Spread by the bite of the sand-fly, it can cause fever, weight loss, enlarged spleen, rash, anaemeia, diarrhoea, fatigue and, left untreated, death.