Hundreds of troops deployed in Sierra Leone and Liberia on Monday to fight the worst outbreak of the deadly Ebola virus, as the death toll climbed to 887 and three new suspected cases of the highly contagious disease were reported in Nigeria.

With health care systems in the West Africa nations completely overrun by the epidemic, the African Development Bank said on Monday it would immediately disburse $50 million to Sierra Leone, Liberia and Guinea — the countries worst affected — as part of an international effort to contain it.

The World Health Organization, which warned last week of catastrophic consequences if the disease were not controlled, reported 61 new deaths in the two days to Friday. The outbreak began in February in the forests of Guinea, where the toll continues to rise, but its epicenter has since shifted to neighboring Liberia and Sierra Leone.