A fast-spreading cholera outbreak has hit Sudan, killing 172 people, with more than 2,500 others becoming ill in the past week. Centered around Khartoum, the disease has spread as many Sudanese who had fled the country’s war return to their homes in the capital and its twin city of Omdurman. There, they often can only find unclean water — a dangerous conduit for cholera — since much of the health and sanitation infrastructure has collapsed amid the fightiing.