The cholera outbreak began in early October 2016.[2][10] The World Health Organization (WHO) considers the outbreak to be unusual in its rapid and wide geographical spread.[11] The earliest cases were predominantly in the capital, Sana'a, with some occurring in Aden.[2] By the end of October, cases had been reported in the governorates of Al-Bayda, Aden, Al-Hudaydah, Hajjah, Ibb, Lahij and Taiz[12] and, by late November, also in Al-Dhale'a and Amran.[13] 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.[14] By mid-January of the following year, 80% of cases were located in 28 districts of Al-Dhale'a, Al-Hudaydah, Hajjah, Lahij and Taiz.[11]
