A shortage of trained staff, operational partners and funding is causing a bottleneck in efforts to expand the Ebola response in the Democratic Republic of Congo as the outbreak spreads geographically, a World Health Organization (WHO) official said on Tuesday.

The outbreak has spread beyond its initial epicentre in Bunia, affecting six provinces and prompting authorities to adopt a more decentralised strategy by building treatment centers closer to newly affected communities, the WHO said.

Congo's outbreak of the Bundibugyo species of Ebola ​has surpassed 3 175 deaths and 6 000 cases, according to the WHO, as the country's worst epidemic continues to spread across ⁠its northeast. 

WHO technical officer Luca Fontana said nearly 1 400 treatment beds had already been established across 59 treatment centres, one of the fastest scale-ups he said he had witnessed, including during the 2014-2016 West Africa Ebola epidemic.

"Yet, despite this extraordinary effort, we estimate that another 1 600 beds will be required," he said.

WHO estimates around three health workers are needed for each Ebola patient bed, meaning around 9 000 staff would be required for the planned capacity of 3 000 beds.

That would require the recruitment and training of roughly 5 000 additional health workers.

Fontana said the pool of international organisations capable of running Ebola treatment centres was limited, partly due to the impact of broader global donor funding cuts.