The year-long Ebola outbreak in the Democratic Republic of the Congo is on the edge of spiralling out of control and the World Health Organization should declare it an international emergency, Rory Stewart, the UK’s international development secretary, has said.

Stewart is on a two-day visit to the DRC visiting emergency health centres and victims of the disease to assess the issues hampering efforts to bring the epidemic under permanent control. So far in the outbreak 2,400 people have contracted the disease and 1,606 have died, according to the WHO.

Militia groups have attacked health workers, and some community leaders say there is resentment over the mass arrival of UN agencies to combat Ebola in a large remote region where for decades more curable diseases such as cholera or measles have been left untreated.

In a Guardian interview, Stewart said: “We are on the edge with this crisis. We keep pulling it back from the brink but it is very dangerous. The very worst-case scenario is if it broke out of the numbers that you could vaccinate. Due to the insecurity, areas that appeared cleared of the disease, such as Beni, have seen the population struck again.”

The WHO has refused three times to declare the outbreak a global health emergency, largely for technical reasons. Stewart said: “I would politely, bearing in mind I have no formal locus in this, encourage them to declare this is a global health emergency, and partly because it will make it easier to raise the extra cash.

“This is definitely a public health emergency. When you are talking to someone with the disease, health workers are stepping away because even with protective equipment people are contracting Ebola and the stories are heartbreaking.”

Quick guide Ebola in the Democratic Republic of the Congo Show Hide How bad is the current outbreak? With more than 2,577 confirmed cases and more than 1,803 confirmed deaths, the outbreak in the eastern DRC is the second largest in history. It has a 67% fatality rate and 11 months after it began, the case numbers are still escalating. It is disproportionately affecting women (55% of cases) and children (28%). The WHO declared the outbreak an international public health emergency in July 2019. The same month saw the the first diagnosis of a case in Goma, a city of 2 million people, which is a transport hub on the border with Rwanda. In early August Rwanda announced that it was closing its border with DRC. The WHO has long said that the national and regional risk levels are very high and containment of the spread to North Kivu and Ituri provinces was unlikely, unless a break in the fighting made it safe for health workers. What is Ebola and how do you treat it? Ebola hemorrhagic fever is caused by a virus that has a reservoir among forest animals, including monkeys and bats. It is spread through body fluids, which is why carers – mostly female relatives and nursing staff – are particularly at risk. It causes fever, aches and diarrhoea and attacks the immune system, causing blood clotting cells to malfunction so that victims bleed extensively and die if their immune system cannot fight off the viral infection. Drugs are still experimental. Patients are isolated and treated by nurses wearing full protective body suits and masks who try to boost their immune response. Friends and relatives are quarantined for 21 days. Prevention measures include washing hands at every opportunity and safe burial practices, with no touching or washing of the body, as is traditional in some cultures. How does this compare with other outbreaks? The 2013 and 2016 outbreak in Sierra Leone, Liberia and Guinea spread for months through forest regions in west Africa where Ebola was unknown before the emergency was recognised. It escalated when it emerged in towns and cities, with 28,600 cases and 11,300 deaths. DRC successfully stamped out nine previous Ebola outbreaks in rural areas within a matter of a few months. Aid agencies, infectious disease experts and the WHO say it will be very hard to bring this outbreak under control, even though they have had vaccines and experimental drugs from the outset. What are the contributing factors to this outbreak? There is almost no functioning state in much of eastern DRC. There is an almost total lack of basic services such as power, education, roads, healthcare, and the authority of the government only extends to the edges of urban areas. Police are corrupt, predatory and violent. In rural zones, militia and armed bands provide security and employment opportunities but also steal, rape and kill at will. It is one of the most hostile environments faced by aid and health workers anywhere in the world. Mistrust of officials and foreigners is harming efforts to tackle the disease and conspiracy theories are rampant. Some believe the outbreak is fake news spread by rapacious NGOs and the UN to justify their presence in the country and allow the extraction of valuable mineral resources. Sarah Boseley and Jason Burke

He singled out some other European countries with links to the DRC for giving “strikingly little”, suggesting France, for example, may have provided as little as $1m (£800,000). The UK and US have provided more than half of the funding for the emergency.

“We are critically short of money,” Stewart said. “There is going to be a funding gap of $100m, and probably of $300m through to December because we have to stay on top of this. It is a very expensive response because the local systems are simply not there. We cannot move from one area to another and say it is solved. It keeps coming out of the periphery again and jumping 300km north. The money is central.”

He said the cash was needed to undertake “ring vaccination”, a way of immunising two layers of contacts of someone who has contracted the disease. During an outbreak in west Africa in 2014-16, one person affected could transmit the disease to as many as four others. The vaccine strategy in Congo can reduce this ratio to 1:1.3. “The only reason we don’t have tens of thousands potentially more dead is because of this British-funded vaccine,” Stewart said.

At the centre of the crisis, in Butembo, Stewart met one recovering Ebola patient, Moise Kambale. His brother had contracted the disease and passed it on to his visiting father, who took it back to Kambale’s family.

“These are unspeakable horrors,” Stewart said. “The critical issue is the way villages and towns respond to the crisis. Thirty percent of people at any one time are terrified about even being vaccinated.

“We were in a healthcare clinic this morning where they have to build an entire sandbag area so when the armed groups come in and start shooting, the healthcare workers can hide.

“This is an area where most of the work has to go into convincing the healthcare workers even to wear their protective clothing, to convince villagers to come forward to be vaccinated, as well as to convince armed groups not to kill doctors. We are struggling to keep up with this.”

He said he was “very concerned” that the disease could spread to the densely populated city of Goma, 200 miles to the south. “If it gets into that kind of place, we have a problem. Goma is really connected to the world. It has the Grand Barriere heading into Rwanda. It is absolutely vital that we hold it here in Butembo and Beni.”

Despite the bravery he saw, Stewart did not shy away from the problems with the emergency response, including a public health system that he said had been destroyed by “decades of predatory government”.

He said: “It is very difficult to work with the infrastructure of the Congo health ministry. There are around 300 small health clinics just around here. Forty percent of the infections in November and December were healthcare workers working inside those health clinics and then passing it on.” He said WHO staff admitted it was very difficult to know what happened in these clinics and were constantly seeking messengers to build trust among local people.

People feel traumatised by the violence that keeps them poor and wonder why the health workers come when so many before have died from disease.

Dr Ibrahima Socé Fall, a senior WHO official in charge of 32 health areas, said: “We have all kind of armed groups here, and just criminals. There are people who want the foreigners to leave and they think if they are in charge it will be an opportunity to make money.”

Fall stayed in Butembo rather than go back to Geneva in an attempt to persuade health workers not to quit after attacks. “We were receiving death threats on WhatsApp on a daily basis. It was very tense. On one occasion there was a rocket through a house.”

David Gressly, the UN response coordinator, said his goal was to introduce real-time information so he could get ahead of the disease and reduce transmissions. One of Gressly’s tasks was to decide whether a second, more plentiful vaccine prepared by Johnson & Johnson should be introduced to supplement the existing Merck vaccine.

'Most complex health crisis in history': Congo struggles to contain Ebola Read more

Stewart said: “In medical terms it is a no-brainer, but there is a very major community problem. This place is awash with rumours. People are very suspicious of the first vaccine. They already think health workers get a different type of vaccine to other people. They are suspicious why the dosage has been reduced or halved.

“The fact is there is an enormous number of people that are very keen to undermine the response because they may be making an incredible amount of money from it. The Mai Mai [the rebel groups] may be connected with the logistics companies or hotels that are making some money from this.

“It is so raw and there are no global answers. It is not useful to come out of this to say we need to focus on governance or transform security or have an integrated multi-stakeholder approach. In the end, yes, you have to do all of those things, but you cannot do any of those things.

“It is about a very imperfect, dangerous world where literally medical staff are in a conference room having a boring meeting and people came in and shot [one of them] twice in the head.”