Humanitarian organisations have warned they are playing “catch-up” as an Ebola epidemic in the Democratic Republic of Congo threatens to become the largest in the country’s history.

The outbreak, which is centred on the eastern city of Beni, has already seen 191 deaths and more than 300 confirmed or probable cases of the haemorrhagic fever identified since August.

Aid workers fear an ongoing armed conflict in the North Kivu province, where Beni is situated, could hamper efforts to reach and treat those living in remote areas.

The World Health Organisation (WHO) has said the epidemic is likely to become the country’s deadliest-ever, surpassing the Yambuku outbreak in 1976 – the first time the virus appeared anywhere in the world.

Beni, a city of 800,000 people where around half of the cases have been identified, has seen its existing treatment centre overrun with patients in recent weeks.

The situation has led humanitarian medical organisation Médecins Sans Frontières (MSF) to hastily build a new clinic to help deal with the outbreak.

“The current treatment centre is overrun and I don’t think anyone expected things would move this quickly in Beni,” MSF project coordinator John Johnson told Sky News.

“What we’re really trying to do now is play catch-up with the epidemic.”

The rate at which new casualties are identified in North Kivu appears to be accelerating, with the city of Butembo, around 35 miles south of Beni, now also increasingly affected by the outbreak.

Neighbouring Uganda has said it will begin to vaccinate some of its health workers against Ebola to prevent the disease spreading across the border.

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The WHO has deployed some 280 staff in North Kivu to support Congolese medical workers, who have administered a new Ebola vaccine to 27,000 people.

“The fact that we have so far prevented Ebola from spreading into neighbouring countries is a testament to the hard work and determination of staff from all partners,” WHO director general Dr Tedros Adhanom Ghebreyesus said.

The US said it was concerned by the outbreak and has sent more than 20 medical workers to Congo to monitor the situation.

However, USAID officials do not believe the situation is currently comparable to the 2014 epidemic in West Africa, where more than 28,000 cases of the disease were identified and 11,000 people died.