In the Democratic Republic of the Congo, nurses and hygiene workers at Ebola treatment centers are risking their lives daily, only to discover that their paychecks are as elusive as a cure for the virus. Sophie Mwadawa Kabundo, a nurse at a treatment center in the northeast, fears she might contract the virus and pass it to her family. 'More and more confirmed cases are being admitted here… Some of our colleagues have died,' she said, adding that they go to sleep worrying about the days ahead as patients pour in.

Her colleague, Martin Bolombi, a hygiene worker at the Elikya treatment centre in Bunia, the capital of the hardest-hit province of Ituri, shares similar fears. 'Personally, this outbreak is causing me a lot of stress,' he said. 'But I have no choice but to pluck up my courage and ensure that the situation is brought under control first, before it can stabilise.' That courage is all the more remarkable given that both workers are among the frontline staff of the fastest-growing Ebola outbreak on record, and they're not being paid.

'I have been working since May and have only been paid for June,' said Bolombi, who was among about 100 people who protested outside the Elikya treatment centre during a strike last month over unpaid bonuses. Kabundo said she was also missing wages. 'We are not being paid and we want the government to provide solutions as soon as possible,' she said. 'We are under immense pressure… We are exposed to the risk of infection, and our families and other loved ones may contract the disease because of us.'

Unpaid wages are just one of the factors - alongside misinformation, community mistrust, and infrastructure deficits - hampering efforts to tackle the outbreak in the DRC, one of the world's poorest countries. More than 2,500 people have now died in the outbreak, which is spreading exponentially in an area larger than France, the senior UN Ebola coordinator, Julien Harneis, said on Friday. Speaking on a video call from Bunia, Harneis called for more aid, saying the existing pool of funds would run out within weeks. He said 160 healthcare workers had fallen ill with Ebola, and 43 of them had died.

'The outbreak is growing faster and wider than the Ebola response,' he added. 'And all of this is happening in an area that has had three decades of conflict and is generating huge humanitarian needs.' The World Health Organization estimates that the outbreak is on course to exceed west Africa's 2014-16 Ebola outbreak as the biggest ever globally. In the previous outbreak, more than 28,600 cases and 11,325 deaths were recorded across Guinea, Liberia, and Sierra Leone, according to WHO data.

The infections in DRC are of the rare Bundibugyo species of the virus. There are no approved treatments or vaccines for the strain, but trials for both are under way. Bolombi said he was working seven days a week, with barely any time to see his family, as the outbreak was getting worse. 'Logistics have improved compared to the early days of the response, but this is still not enough, as needs are growing as the disease progresses,' he said.

Despite the enormous challenges and lack of remuneration, Kabundo expressed pride that there had been 'a large number of recoveries' at the Elikya treatment centre. 'This progress must be highlighted, but it is no excuse to rest on our laurels,' she said. The Congolese health ministry did not immediately respond to a request for comment.

Ebola is transmitted to people from wild animals and then spreads between humans via direct contact with the organs, blood, or other body fluids of infected people, including dead bodies. It can also be spread through contact with contaminated surfaces and materials, such as bedding or clothing. Initial symptoms can include fever, fatigue, muscle pain, headaches, and a sore throat. These progress to vomiting, diarrhoea, abdominal pain, rash, and symptoms of impaired kidney and liver functions.

Widespread mistrust and misinformation have resulted in people with the virus not attending health centres for treatment until it is too late, as well as attacks on health facilities and ambulances. Dr Eddy Kambale Kahandukya, a deputy medical coordinator for the charity Médecins Sans Frontières in the DRC, said: 'The lack of community engagement remains a major challenge in breaking this chain of transmission… For example, patients who suspect they have symptoms and are awaiting laboratory results seek refuge within the community and end up creating new clusters that further fuel the spread of the epidemic.'

Fear was a big driver of the lack of trust in the authorities' response to Ebola, said Manon Dumortier, an emergency coordinator in Bunia for the aid group Mercy Corps. 'It's scary, right? … Suddenly there are so many people dying and you don't know what it is about,' she said. 'People are just disappearing, going to health centres and you cannot even see them before they are being buried. This is just raising a lot of speculation and rumours.'

The WHO declared the outbreak a public health emergency of international concern in May, but later said sequencing showed the outbreak had started months earlier in February. The virus has spread to six of the DRC's 26 provinces, concentrated in the country's north-east. More than 4,200 of the confirmed cases are in Ituri, which borders Uganda and South Sudan. Uganda reported 20 cases and two deaths, all in the capital, Kampala. The government declared the country Ebola-free on 28 July after the last Ebola patient, a Congolese national, was discharged on 16 July.