countries from the Middle East and Africa, in response to calls from President Abdrabbuh Mansur Hadi for military support. Cholera is an infection of the small intestine by strains of the bacterium Vibrio cholerae. It is spread mostly by unsafe water and unsafe food that has been contaminated with human feces containing the bacteria. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea lasting a few days. Diarrhea can be so severe that it leads, within hours, to severe dehydration and electrolyte imbalance. The primary treatment is oral rehydration therapy—the replacement of fluids with slightly sweet and salty solutions. In severe cases, intravenous fluids may be required, and antibiotics may be beneficial. Prevention methods against cholera include improved sanitation and access to clean water. Cholera vaccines that are given by mouth provide reasonable protection for about six months. Two oral killed vaccines are available: Dukoral and Shanchol. Total cost, including delivery costs, of oral cholera vaccination is under US$10 per person. Outbreak Following "on the heels of civil conflict between Houthi rebels and the internationally recognized Yemeni regime", the Yemen cholera outbreak began in early October 2016, and by January 2017, the WHO Regional Office for the Eastern Mediterranean (WHO EMRO) considered the outbreak to be unusual in its rapid and wide geographical spread. The serotype of vibrio cholerae O1 involved is Ougawa. The earliest cases were predominantly in the capital, Sana'a, with some occurring in Aden. By the end of October, cases had been reported in the governorates of Al-Bayda, Aden, Al-Hudaydah, Hajjah, Ibb, Lahij and Taiz and, by late November, also in Al-Dhale'a and Amran. By mid-December, 135 districts of 15 governorates had reported suspected cases, but nearly two-thirds were confined to Aden, Al-Bayda, Al-Hudaydah and Taiz. By mid-January 2017, 80% of cases were located in 28 districts of Al-Dhale'a, Al-Hudaydah, Hajjah, Lahij and Taiz. A total of 268 districts from 20 governorates had reported cases by 21 June 2017; over half are from the governorates of Amanat Al Asimah (the capital Sana'a), Al-Hudaydah, Amran and Hajjah, which are all located in the west of the country. In particular, 77.7% of cholera cases (339,061 of 436,625) and 80.7% of deaths from cholera (1,545 of 1,915) occurred in Houthi-controlled governorates, compared to 15.4% of cases and 10.4% of deaths in government-controlled governorates. Using genomic sequencing, researchers at the Wellcome Sanger