New cases and deaths from the Ebola virus outbreak in the West African countries of Guinea, Liberia and Sierra Leone, already the worst ever recorded for the disease, have surged by double-digit percentages in the past week, the World Health Organization reported Tuesday, with no sign of a slowdown. Alarmed Ivory Coast border authorities blocked hundreds of Ivorian refugees in Liberia from returning, news agencies reported.

In its latest update, the W.H.O. said the number of suspect, probable and confirmed cases as of Saturday totaled 964, up about 14 percent from a week earlier. Deaths totaled 603, up about 16 percent from a week earlier. Half the deaths have been in Guinea.

“This trend indicates that a high level of transmission of the Ebola virus continues to take place in the community,” the W.H.O. said in the update. “The respective ministries of health are working with W.H.O. and partners to step up outbreak containment measures.”

The latest figures were reported as the W.H.O. helped complete a coordination center in Conakry, Guinea’s capital, in an attempt to slow the spread of Ebola, a hemorrhagic fever with no known cure and a death rate that can reach 90 percent. The virus first appeared in 1976 near the Ebola River in the Democratic Republic of Congo and is believed to have been spread originally by fruit bats. Gorillas, chimpanzees, forest antelopes and porcupines can also spread the virus.