GENEVA, Switzerland (AFP) — The Ebola outbreak in the Democratic Republic of Congo (DRC) is intensifying at an "exceptional" pace, the World Health Organization (WHO) warned on Saturday, calling for a significant scaling-up of the health response.

"This outbreak is now the largest recorded Ebola virus disease outbreak in the country," the WHO said in a statement.

The deadliest Ebola outbreak in the DRC killed nearly 2,300 out of almost 3,500 recorded cases between 2018 and 2020.

The current outbreak was declared on 15 May and is caused by the Bundibugyo strain of the virus, for which there is no approved vaccine or treatment.

As of 30 July, a total of 3,605 confirmed cases, including 1,587 deaths, had been reported in the DRC, according to the WHO, indicating a case fatality rate of 44 percent.

The outbreak is "intensifying, with sustained transmission and continued increases in reported cases and deaths," the WHO warned.

Ebola, which spreads through contact with bodily fluids and causes hemorrhagic fever, has killed more than 15,000 people across Africa over the past 50 years.

The center of the current outbreak is the northeastern Ituri province, which borders South Sudan and Uganda.

The virus has also spread to four other provinces including North Kivu and South Kivu where provincial capitals and large swathes of land are controlled by the Rwanda-backed M23 armed group.

"The convergence of insecurity, population displacement and mobility, and cross-border movements complicate response operations and increase the risk of further geographical spread," the WHO said.

A vaccine described by the WHO as the "most promising" to fight the current outbreak will be developed by Singapore-based Hilleman Laboratories, it announced on Thursday.

Last week, a first volunteer received the first dose of a different Bundibugyo vaccine being developed by Oxford University under a clinical trial.