Thousands of new Ebola cases are likely to surface in the coming weeks in Liberia, the hardest-hit nation in the widening epidemic in West Africa, the World Health Organization said. The UN health agency said the disease may infect as many as 20,000 people, and will take six to nine months to contain. The outbreak, the worst in almost 40 years, has so far killed about 2,100 people, more than half of them in Liberia. Other countries hit include Sierra Leone, Guinea, and Nigeria. WHO said in a statement that “the number of new cases is increasing exponentially.” Fourteen of Liberia’s 15 counties have reported confirmed cases, and Ebola treatment centers immediately overflow with patients as soon as they open.