Senior U.S. health officials met with high-ranking officials from Guinea, Liberia and Sierra Leone Monday and held “intensive” talks on how best to mount an effective defense against the worst Ebola outbreak in history.

The death toll increased from 729 to 887 deaths in Guinea, Sierra Leone, Liberia and Nigeria, the World Health Organization announced Monday. U.S. President Barack Obama is hosting more than 50 leaders from across Africa in Washington, D.C. this week. However, the heads of state of Guinea, Liberia and Sierra Leone cancelled plans to attend due to the outbreak of Ebola in their countries.

“This cluster of cases in Lagos, Nigeria is very concerning,” Dr. Tom Frieden, director of the U.S. Centers for Disease Controls and Prevention, told the Associate Press. “It shows what happens if meticulous infection control, contact tracing, and proper isolation of patients with suspected Ebola is not done. Stopping the spread in Lagos will be difficult but it can be done.”

In Liberia, the number of cases rose from 156 to 255 as the government ordered all Ebola victims be cremated because of rising opposition to burials in neighborhoods around the capital.

In Sierra Leone, Monday marked a national stay-at-home day to try and halt the disease’s spread.

In Nigeria, authorities said 70 people were under surveillance and that they hoped to have eight people in quarantine by the end of Monday.

The CDC is sending 50 experienced disease control specialists to West Africa.

From the State Department Monday:

U.S. Secretary of Health and Human Services (HHS) Sylvia Mathews Burwell, and Centers for Disease Control and Prevention (CDC) Director Dr. Tom Frieden consulted today with the President of Guinea Alpha Condé, and senior officials from Liberia and Sierra Leone about the outbreak of Ebola in West Africa. The group identified national and regional priorities and held intensive discussions on the types of assistance needed to mount an effective response. Secretary Burwell and Director Frieden reiterated U.S. engagement and support for efforts to control the outbreak and address the challenge. The discussions took place on the margins of the U.S.-African Leaders Summit now taking place in Washington.