Democratic Republic of Congo said on Tuesday that confirmed Ebola deaths had reached 2 011, the latest grim milestone in what health officials have described as the fastest-spreading outbreak on record.

The latest data from Congo's public health institute, seen by Reuters, also reported 4 381 confirmed cases across five provinces.

Delayed detection, conflict and strained health services have helped the virus spread more rapidly than in previous outbreaks.

The current outbreak, Congo's 17th, is caused by the Bundibugyo strain of Ebola, for which there are no approved vaccines or treatments.

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

A study published last month in the journal Science found that transmission may have begun in January or earlier in Ituri province, identifying more than 500 suspected cases between mid-January and May 15.

Shortages of medical supplies and insecurity in affected areas have complicated efforts to trace contacts, isolate patients and curb transmission.

The Congolese government data shows that only West Africa's 2014 to 2016 Ebola outbreak was bigger, with 28 616 cases and 11 310 deaths recorded across ​Guinea, Liberia and Sierra Leone, according to the World Health Organization.

It took nearly five months from the declaration of that outbreak to hit 1 000 deaths, whereas Congo's current outbreak has hit 2,000 deaths in less than three months.

In an Ebola outbreak in Congo from  2018 to 2020, it took a little over 12 months to hit 2 000 deaths. In the current outbreak, deaths have jumped from 1 000 to 2 000 in less than a month, further underscoring how quickly the virus is spreading.