The United Nations says the cholera death toll in Zimbabwe has risen to over 1,500 and case fatality rates are increasing. The World Health Organization says 1,518 people have now died and a total of 26,497 cases have been recorded since the start of the outbreak in August. The U.N. agency's figures indicate that more than two-thirds of deaths occurred in December alone. The percentage of cholera patients dying from the disease has risen to 5.7 percent from 4 percent at the beginning of the month. The agency said in an update posted on its Web site Friday that the outbreak is not yet under control. It recommends neighboring countries scale up disease monitoring and preparedness but refrain from mass vaccination campaigns.