May 21 (UPI) -- A cholera outbreak in war-torn Yemen has killed 315 people since April 27 and is spreading with "unprecedented" speed, the United Nations' World Health Organization said Sunday. More than 29,300 suspected cases have been reported in 19 of the country's 22 provinces, the agency posted on Twitter. The highest number of likely cases -- more than 6,000 -- are in the capital city, Sana'a, where the Houthi government declared a state of emergency one week ago. On Friday, the WHO warned that Yemen could have as many as 300,000 cases of cholera within six months and an "extremely...