DRC’s Ebola virus outbreak likely to become worst in history, WHO says. Here’s why

The Ebola outbreak taking place in the Democratic Republic of Congo (DRC) is on track to become the deadliest on record, according to the director-general of the World Health Organization.

“It is already the second-biggest Ebola epidemic on record, and it is moving faster than any previous Ebola outbreak,” Tedros Adhanom Ghebreyesus said on Wednesday.

The highly transmissible virus, which causes sudden flu-like symptoms before progressing to vomiting, diarrhoea and potential organ failure, has overwhelmed the health system in the DRC’s north-east, a part of the world already gripped by armed conflict and food insecurity.

But there are fears the virus could spread well beyond the region’s borders, with the majority of new infections outpacing contact tracers and cases already detected in neighbouring Uganda.

Here are five reasons the outbreak is proving so difficult to contain and key graphs that put the size of the task into perspective.

Health authorities are ‘playing catch-up’

Dr Tedros said unless health authorities were able to drastically scale up their testing, contact tracing and isolation efforts, the death toll was almost certain to eclipse that of the Ebola epidemic that devastated West Africa a decade ago.

That outbreak, which took place from 2014 to 2016 across Guinea, Liberia and Sierra Leone, led to the deaths of at least 11,308 people from 28,610 infections, making it the deadliest in history.

As of Friday, the DRC’s outbreak had caused 2,214 deaths from 4,727 confirmed infections, 85 per cent of which had occurred in the north-eastern Ituri province, the outbreak’s epicentre.

But while the current death toll is yet to reach 20 per cent of the West African epidemic total, it is the pace of deaths and infections that is concerning health authorities.

This outbreak took just 37 days to reach 250 deaths, while the West African outbreak took 78 days to hit that number. Another outbreak in the DRC, which took place from 2018 to 2019, took 130 days to reach the same milestone.

Similarly, this outbreak surpassed 1,000 confirmed cases within just 38 days of the first case being confirmed, while, the 2018 Ebola outbreak in DRC took more than 230 days to do so.

Researchers now believe the current outbreak began two or three months before it was officially declared on May 15, with some cases of malaria and typhoid diagnosed in February likely to have been misdiagnosed instances of Ebola.

‘Hidden’ transmission evading trackers

Central to the pessimism surrounding the virus’s current trajectory is the evidence that actual case numbers far exceed the official number of confirmed cases.

In July, more than 80 per cent of new cases presenting for treatment were unable to be linked to known contact lists, a sign of high levels of community transmission taking place outside of authorities’ knowledge.

Those unknown transmission chains will need to be identified and interrupted if authorities are to have any chance of bringing the epidemic under control.

While the WHO is highlighting improved contact-tracing rates — the rate at which known contacts of existing cases are being checked up on daily — it will have limited effect if the outbreak is being driven by transmission outside those networks.

The majority of deaths caused by the virus have also consistently been occurring in the community, rather than inside treatment centres, both driving home the likelihood of “hidden” community transmission and compounding the problem due to the unsafe handling of bodies.

In addition to the virus’s head start due to likely misdiagnoses, contact tracers are also playing catch-up due to an initial lack of rapid testing kits for this strain of Ebola, known as the Bundibugyo virus.

In late April, when the first suspected cases of Ebola surfaced in Bunia, Ituri’s capital, the samples that were tested came back negative because the kits were designed to detect only the more common Zaire strain of the virus, responsible for the 2014–16 epidemic.

Now, a backlog of samples and a shortage of reagent chemicals needed to test the Bundibugyo strain is leading to further delays in diagnosis, making it more difficult to isolate suspected cases.

Workers are underpaid and often in danger

The challenges of tracing the virus, while formidable, are put into perspective when compared to those faced by the health workers tasked with treating it.

Public health authorities in the DRC are woefully under-resourced and overwhelmed by growing case numbers.

Many workers have gone on strike after not having been paid in months, which the government says is the result of logistical issues exacerbated by the outbreak.

Outside experts also point to funding shortfalls caused by drastic cuts to international aid budgets, leading to a lack of international specialty staff in Ebola clinics.

Even in Bunia, where the medical response is most visible, many health workers lack basic protective equipment, putting themselves at risk as they interact with patients.

Dozens of health workers have already died in this outbreak, and once infections occur in a healthcare setting, the hospital or clinic in question is often forced to close for deep cleaning.

These are the problems facing health workers in Ituri’s cities, where they are able to go about their jobs largely unhindered.

That is not the case elsewhere in the country’s east, which prior to the epidemic was already considered one of the most volatile regions in Africa.

An ongoing civil war, involving dozens of armed groups including the Rwanda-backed M23 rebels and the Islamic State-linked Allied Democratic Forces, makes free travel throughout the region next to impossible.

Militia-run checkpoints dot the damaged roads that connect Ituri’s thousands of small villages, and government health workers are viewed with suspicion.

If those workers are allowed access to infected communities, treatment clinics are sometimes attacked by angry locals who believe Ebola is a ruse to make money, or is caused by witchcraft rather than a virus.

Traditional Congolese funerals — days-long events in which family members often wash, dress and cry over the body of their loved ones — have also been identified as mass spreaders of the disease, which is transmitted through bodily fluids that remain infectious after death.

Safer burials run by health workers are often protested or disrupted by the deceased’s family and friends.

Mass movement is a fact of Congolese life

Another core difficulty facing DRC authorities is the difficulty of preventing mass movement within their country’s borders, let alone incidental travel out of infected provinces.

While Ituri remains the epicentre of the DRC’s outbreak, sustained community transmission has been recorded in four other provinces: Nord-Kivu, Sud-Kivu, Haut-Uélé and Tshopo, sometimes in areas hundreds of kilometres away.

The Africa Centres for Disease Control and Prevention confirmed on Thursday that a man had also died of Ebola in a sixth province, Bas-Uélé, while 20 cases had been recorded in Uganda, across the border to the east, as of July 28.

A key concern for international observers is that the DRC shares a border on its north-east with South Sudan, which is itself on the brink of civil war and suffering the same lack of adequate health infrastructure as its neighbour.

While no cases have yet been confirmed in the country, the aid group Mercy Corps revealed on Thursday that cases had been detected in three Congolese cities along a major northern travel corridor into South Sudan, presenting a major risk of escalating the outbreak.

“Almost three months since this outbreak was officially declared, its speed and scale are staggering, and the risk of cross-border spread is growing,” said the group’s DRC director of humanitarian programs, Lancelot Mermet.

The civil war raging in the DRC’s east is a key reason for the mass movements observed within the country, which has one of the largest populations of internally displaced people in the world.

About 900,000 people from Ituri alone are living in refugee camps after fleeing violence in the province.

Many workers are forced to support their families by travelling between the region’s many small-scale, largely unlicensed gold mines, making them reluctant to isolate or engage with health authorities.

Prior to the outbreak, up to 600 Congolese refugees per day were also crossing the border into Uganda, and UN refugee agencies say that flow has not diminished since the epidemic was declared.

Notably, the WHO is advising neighbouring countries not to close their borders with the DRC or impose travel restrictions, as they could run the risk of encouraging clandestine border crossing or discouraging the reporting of cases.

The Ebola outbreak itself is now believed to be one of the many factors driving mass movement within the DRC, with aid workers and soldiers at checkpoints witnessing “waves” of people fleeing areas hardest hit by the virus.

It’s called ‘walking Ebola’ for a reason

The big question on everyone’s mind is when daily infection numbers will stop growing.

Speaking on Thursday, Abdirahman Mahmud, the WHO’s director of alert and response coordination, said the UN agency expected this Ebola outbreak to peak in about six months.

“But … that’s the moderate scenario,” Dr Mahmud said.

A quirk of Ebola’s Bundibugyo strain, however, means the make-up of the virus itself could be a factor in the current outbreak’s projected longevity.

A meta-analysis published in the Journal of Infection and Public Health in 2024 looked at the historical rate at which an infection led to death for different strains of Ebola, including the Zaire, Sudan and Bundibugyo strains.

Between 1976 and 2022, outbreaks of the Zaire strain resulted in an average CFR (case fatality ratio) of roughly 66.6 per cent, making it the most lethal strain of the virus (some individual outbreaks recorded CFRs of almost 90 per cent).

The Sudan strain averaged a CFR of 48.5 per cent over that same period, while Bundibugyo averaged 32.8 per cent.

The current outbreak’s CFR is sitting at about 46.8 per cent, higher than some recent Sudan strain outbreaks.

However, researchers believe this figure will likely come down, as they point the finger at delayed detection and challenging conditions on the ground for the higher initial death rate, rather than this being a more lethal pathogen.

Counterintuitively, the fact the Bundibugyo strain is slightly less deadly than its peers may actually make it a more formidable threat as an epidemic.

While its incubation period of two to 21 days is similar to that of the Zaire and Sudan strains, the Bundibugyo strain replicates more slowly, meaning it takes longer to attack the body’s immune system after an infection.

That’s good news for the infected person — they have a greater chance of obtaining medical treatment before their symptoms worsen — but potentially bad news for society, as it allows for a considerable period in which patients are sick enough to spread the virus, but not so sick they cannot move through the community.

It’s why the Bundibugyo strain has been nicknamed “walking Ebola”.

The rarity of Bundibugyo outbreaks is also likely the reason there are no approved vaccines for the strain — though human trials of an Oxford candidate are now taking place.

Like many aspects of this epidemic, those involved are in a race against time.

Fourteen people have so far received the jab, which uses the same vaccine platform that was used to develop the Oxford AstraZeneca COVID vaccine.

The study is still recruiting volunteers.