Data published overnight into Tuesday showed the outbreak has recorded a total of 4381 confirmed cases in the Democratic Republic of the Congo, including 2011 deaths.
A total of 704 patients are in admission and isolation.
The grim toll comes nearly three months since the outbreak was declared on May 15.
While it took about nine weeks for the outbreak to record 1000 deaths, it's taken only about three weeks to record the additional 1000 deaths, showing how fast the health crisis is moving beyond the control of responders.
It's already the second-largest outbreak in history, only behind the 2014-2016 West Africa outbreak that recorded more than 28,000 cases including over 11,000 deaths.
Aid workers say the outbreak continues to outpace response that's been expanding across the five provinces affected.
Many health workers have gone on strike to protest lack of payment for their work since the outbreak was declared. And most new cases are recorded outside of contacts being monitored.
The Ebola outbreak is unlike most previous ones because the rare Bundibugyo virus responsible for it has no approved vaccines or treatments.
Clinical trials for those have begun in Ituri, the epicentre of the outbreak.
The World Health Organisation said on Monday that the outbreak likely started in February, long before authorities detected it in one of Congo's most remote and vulnerable areas.
WHO said some cases early on were wrongly attributed to malaria and typhoid, and that early testing was conducted for the more common type of Ebola.
The WHO regional director for Africa, Dr Mohamed Yakub Janabi, told a news conference that officials were "chasing the virus, the virus is ahead of us".
The first Ebola virus to be identified was in 1976 near the Ebola River in what is now Congo.
The outbreak is the 17th - and largest - the Central African nation has faced.
