GENEVA — The U.N. health agency says there have been 50 new Ebola cases in Sierra Leone and Liberia since last week as the disease, among the deadliest in the world, keeps spreading in West Africa.

The World Health Organization says 34 new cases were reported by Sierra Leone and 16 by Liberia since July 3.

WHO officials said in a statement Tuesday the outbreak in those two countries and Guinea shows "a mixed picture" because of a reduction in the number of new cases in Guinea, where no new cases have been reported during the past week.

The agency says as of Sunday, there have been 844 cases of Ebola in the three countries, including 518 deaths.