The Ebola outbreak in the Democratic Republic of the Congo has become the "fastest growing" in history, African health authorities said Thursday, as the World Health Organization reported that the death toll had climbed to 600.

Updated figures from the U.N. health agency showed 1,759 confirmed Ebola cases since the outbreak was declared in mid-May, including 600 confirmed deaths.

"This is the fastest growing Ebola outbreak ever, not only among previous Bundibugyo outbreaks, but across all Ebola virus strains," Wessam Mankoula, head of emergency preparedness and response at the Africa Centres for Disease Control and Prevention, told reporters.

Mankoula said the current outbreak has spread at an unprecedented pace, surpassing even the deadliest Ebola epidemic on record in West Africa between 2013 and 2016.

That outbreak recorded 994 cases during its first six weeks, compared with 1,596 cases over the same period in the current outbreak.