Bunia, Congo — At least 2,000 people have died among the confirmed cases in Congo’s Ebola outbreak that is the fastest-spreading on record, according to the latest government data, as health authorities struggle to get help quickly to remote localities due to rebel conflict, bad roads and work stoppages over payment issues.

Data published overnight into Tuesday showed the outbreak has recorded a total of 4,381 confirmed cases, including 2,011 deaths.

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 1,000 deaths, it’s taken just around three weeks to record the additional 1,000 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.

The World Health Organization has declared the outbreak, which has also led to cases in neighboring Uganda, a public health emergency of international concern.  

Aid workers say the outbreak continues to outpace the response that’s been expanding across the five provinces affected. Many health workers have gone on strike to protest not being paid for their work since the outbreak was declared. And most new cases are recorded outside of contacts that are 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 epicenter of the outbreak.

The WHO 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 are “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 current outbreak is the 17th — and largest — the Central African nation has faced.