MAIDUGURI, June 10 -- The deaths in Borno this time are not from bombs or bullets. They are from water. A cholera outbreak tearing through Nigeria's northeastern Borno state has killed at least 74 people and infected nearly 8,000 since early May, the medical charity reported this week, overwhelming a health system already broken by 17 years of war. The toll has roughly doubled in a week, and with more than 500 patients admitted on the worst single day, those dying are overwhelmingly the people a long insurgency had already stripped of everything else.

The figures, drawn from the state health ministry, count 7,850 suspected cases across 14 local government areas as of June 7. Doctors Without Borders says it has treated more than 7,400 pat...