The UN agency says that although efforts to stop the virus spreading are working, it is proving hard to keep track of where the virus is active.
Four new cases surfaced last week in people who did not appear to have come into contact with other infected patients, causing concern for health workers.
The official warning came just days after the death toll rose to 78 in the central African country on August 28.
There have been 86 confirmed cases of the deadly infection since the outbreak began on August 1, with dozens more suspected.
The DRC’s Ebola outbreak is now entering its second month and the WHO said on Friday ‘substantial risks’ remain in trying to control the virus.
Global health officials said that while control measures appear to be working, health officials are still unable to track exactly where the deadly virus is spreading.
Four of the 13 new cases from the city of Beni were not previously identified as contacts, meaning officials don’t know how they were exposed to Ebola.
An important part of preventing the spread of the virus is monitoring people who have been in contact with others infected with the fever, to make sure they don’t develop symptoms and spread the infection.
If people develop the infection without coming into contact with previous patients it could mean the virus is coming from elsewhere.
This makes it harder for health workers to track down and contain all the sources of the fast-spreading disease.
The WHO also reports ‘sporadic instances’ of high-risk behaviors like unsafe burials, which could worsen the outbreak because Ebola can still be caught from corpses.
The UN health agency in a new statement said most patients recently admitted to Ebola clinics were given experimental treatments and that many contacts of cases have been immunized with a novel vaccine.
Ebola can be fatal in up to 90 per cent of cases
Ebola is a haemorrhagic fever which causes sudden fever, vomiting, diarrhoea and internal and external bleeding.
The virus can be fatal in up to 90 per cent of cases, depending on the strain, and spreads quickly between people through contact with infected bodily fluids.
Last week, two of the first 10 people to have been given an experimental cure known as mAb114 made a recovery from the often-deadly infection.
In a statement the DRC’s health ministry confirmed: ‘These two people are among the first 10 patients to have received the therapeutic molecule mAb114.’
Treatment usually relies on keeping patients hydrated and quarantined, and trying to manage their symptoms as the body tries to fight off the virus.
Developed in the US, mAb114 was the first of five experimental treatments the DRC has begun using in the outbreak.
The health ministry has confirmed four other experimental drugs have been approved for use in the country – ZMapp, Remdesivir, Favipiravir and Regn3450-3471-347.
More than 100 people are thought to still be living with Ebola in the area.
Ebola, a haemorrhagic fever, killed at least 11,000 across the world after it decimated West Africa and spread rapidly over the space of two years.
That pandemic was officially declared over back in January 2016, when Liberia was announced to be Ebola-free by the WHO.
The country, rocked by back-to-back civil wars that ended in 2003, was hit the hardest by the fever, with 40 per cent of the deaths having occurred there.
Sierra Leone reported the highest number of Ebola cases, with nearly of all those infected having been residents of the nation.
WHERE DID IT BEGIN?
An analysis, published in the New England Journal of Medicine, found the outbreak began in Guinea – which neighbours Liberia and Sierra Leone.
A team of international researchers were able to trace the pandemic back to a two-year-old boy in Meliandou – about 400 miles (650km) from the capital, Conakry.
Emile Ouamouno, known more commonly as Patient Zero, may have contracted the deadly virus by playing with bats in a hollow tree, a study suggested.
Aid workers will have to work among more than 100 armed groups
Yet, he also raised fears that conflict in the region might make the outbreak hard to control, as those infected could be displaced to refugee camps where the virus can thrive.
Professor Hunter said: ‘The effectiveness of any immunisation campaign depends on the ability to deliver that vaccine to the appropriate people is a timely manner.
‘Unfortunately the latest outbreak is in an area of armed conflict and this poses substantial difficulties for effective prevention.’
Aid workers have been told they will have to navigate their response among more than 100 armed groups.
A WHO spokesperson said: ‘This is an active conflict zone. The major barrier will be safely accessing the affected population.’
Figures show nearly 29,000 people were infected from Ebola – meaning the virus killed around 40 per cent of those it struck.
Cases and deaths were also reported in Nigeria, Mali and the US – but on a much smaller scale, with 15 fatalities between the three nations.
Health officials in Guinea reported a mysterious bug in the south-eastern regions of the country before the WHO confirmed it was Ebola.
Ebola was first identified by scientists in 1976, but the most recent outbreak dwarfed all other ones recorded in history, figures show.
HOW DID HUMANS CONTRACT THE VIRUS?
Scientists believe Ebola is most often passed to humans by fruit bats, but antelope, porcupines, gorillas and chimpanzees could also be to blame.
It can be transmitted between humans through blood, secretions and other bodily fluids of people – and surfaces – that have been infected.” id=”
HOW MANY PEOPLE WERE STRUCK DOWN?
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