The Ebola outbreak in the Democratic Republic of the Congo has been spreading there for a year, and American federal officials reported Thursday that the deadly virus is showing no sign of abating.

“It appears the outbreak continues at the same pace, so we don’t see evidence of slowing,” Dr. Henry Walke, who is leading the response for the Centers for Disease Control and Prevention, said in a call with reporters. “We remain concerned and continue to try to have an impact on the response.”