Ebola may have been spreading in DRC weeks before it was detected

Health workers simulate evacuation protocols using a manikin for deceased victims of Ebola during a training by Médecins Sans Frontières (MSF) in Ongata Rongai, Kajiado County, on July 10, 2026. [AFP]

The Ebola outbreak in the Democratic Republic of Congo may have been underway for weeks before health authorities knew they were dealing with the virus, raising fresh questions about how much transmission can occur before an outbreak becomes visible. A study has revealed.

The possibility has emerged from epidemiological investigations into the current outbreak, which was formally declared on May 15 after laboratory confirmation in Ituri Province.

By then, however, investigators believe the virus may already have been circulating in communities.

A clinical review published in the New England Journal of Medicine (NEJM) says investigations indicate that transmission probably began several weeks before the outbreak was officially recognised, including possible transmission linked to people handling the bodies of deceased patients.

That distinction is critical in an Ebola outbreak. The date authorities announce an epidemic is rarely the same as the date the virus began spreading.

In the DRC, investigators are now working backwards through patient histories, unexplained deaths, contact networks and viral sequencing to establish how far the virus may have travelled before the first cases were identified.

“The 2026 Bundibugyo virus outbreak has highlighted persistent challenges in detection, surveillance and the availability of effective countermeasures for Ebola species beyond Zaire Ebola virus,” said Dr Nancy J. Sullivan, ScD, one of the authors of the NEJM review, according to the material reviewed.

The investigation has also drawn attention to a possible early transmission event in February.

Reuters has reported that investigators are examining a funeral in Mongbwalu involving a man who died in February. More than 80 people reportedly attended, with relatives handling the body after it was transported in a damaged coffin. The event remains under investigation and has not been established as the source of the outbreak.


That uncertainty is important.

Finding an early transmission event does not necessarily identify where an outbreak began. Ebola investigations often reconstruct the earliest stages of an epidemic only after cases begin appearing in numbers large enough to trigger investigation.

The first recognised case in this outbreak was a nurse who died in April in Mongbwalu, Ituri Province. Other healthcare workers who had cared for patients at the same facility later developed compatible symptoms.

By the time that signal became clear, the virus had already had an opportunity to move.

And that is where the danger of delayed detection lies.

Ebola can initially resemble illnesses that are common across much of tropical Africa. Fever, weakness, headache, muscle pain, vomiting and diarrhoea are not unique to Ebola and can initially be mistaken for malaria or other infections.

A patient may therefore seek treatment without Ebola immediately being suspected. Family members may provide care at home. Health workers may come into contact with an infected person before the diagnosis is known.

In some communities, relatives may also handle the body of someone who has died.

Each of those encounters can create another opportunity for transmission.

The scale of the outbreak now confronting DRC shows what can happen when those early signals are missed.

As of August 11, Congolese authorities had reported 4,450 confirmed cases and 2,063 confirmed deaths. The outbreak has spread across five provinces.

That places the epidemic among the largest Ebola outbreaks ever recorded and makes the question of when transmission actually began more than an academic exercise.

Every infection detected late potentially means more contacts to trace. Every unidentified contact creates another gap in surveillance.

And every unexplained death makes it harder for investigators to reconstruct the chain of transmission.

WHO Regional Director for Africa Mohamed Yakub Janabi has captured the difficulty confronting response teams bluntly.

“We are chasing the virus, the virus is ahead of us,” Janabi said, according to reporting from a UN briefing.

He has also called for urgent protection of Bunia, where patients from surrounding areas are increasingly seeking treatment.

“We have to protect Bunia now,” Janabi said, while calling for treatment capacity to be expanded outside the city.

The concern is not only how many people have become infected, but how many infections may still be invisible.

Investigators are using patient histories, unusual clusters of illness and deaths, contact tracing and genomic sequencing to piece together the outbreak's earlier stages.

The scientific evidence also suggests that the virus responsible for the current epidemic is genetically distinct from the Bundibugyo virus associated with Uganda's 2007 outbreak and is more closely related to the strain involved in the 2012 DRC outbreak. The findings point towards a new zoonotic transmission event.

That makes the timeline even more important.

If transmission began weeks before the outbreak was recognised, strengthening surveillance after confirmation will not be enough. Public-health systems must also become better at identifying unusual patterns before they develop into obvious outbreaks.

For Kenya, this is perhaps the most important lesson.

Kenya has raised its Ebola preparedness to nearly 90 per cent, with surveillance, laboratory capacity, infection prevention and control measures and health-worker training strengthened.

But preparedness is ultimately tested before a disease receives a name.

A patient arriving at a Kenyan health facility with fever, vomiting or diarrhoea may not immediately appear to have Ebola. The critical question is whether the health worker has the tools and information to recognise the possibility, ask about travel and exposure, and trigger testing before further contacts are exposed.

The DRC experience also shows why preparedness cannot be reduced to isolation centres and emergency stockpiles.

It depends on frontline workers recognising unusual illness, laboratories confirming cases quickly, surveillance teams finding contacts and communities trusting health authorities enough to report illness and cooperate with investigations.

The consequences of delayed detection can extend beyond those infected.

In the current outbreak, a nurse was among the earliest recognised casualties. Health workers can become exposed before the disease is identified, while families and communities can become part of transmission chains before public-health teams understand what is happening.

The humanitarian environment makes the task even harder.

Conflict and displacement in eastern DRC have complicated access to communities and health services, while the United Nations has called for additional resources and sustained humanitarian access to support the response.

At the same time, scientists are racing to find treatments for a virus for which far fewer medical countermeasures are available than for the Zaire species of Ebola.

The WHO-sponsored PARTNERS trial is evaluating remdesivir and the monoclonal antibody MBP134, including their use in combination, to determine whether they can help patients infected with Bundibugyo ebolavirus.

Prof Laurens Liesenborghs of the Institute of Tropical Medicine in Antwerp, one of the researchers involved in the trial, said the drugs had already produced encouraging results in animal studies.

“These two drugs actually have been proven to work against the Bundibugyo virus in animal models. They showed great efficacy, but now we need to test it in humans,” Liesenborghs said.

The speed of the research response is itself a significant change from the last major Ebola crisis.

During the 2014–2016 West Africa epidemic, clinical trials took more than a year to get under way. This time, researchers moved into clinical testing within weeks.

Prof Amanda Rojek, a University of Oxford researcher and international principal investigator of the PARTNERS trial, said: “If we look back at West Africa, where it took us over a year to start clinical trials, we're very proud of the team led by INRB that we've managed to achieve that in six weeks since the outbreak was first announced.”

But even rapid research cannot reverse infections that have already occurred.

That is why the most consequential finding from the DRC outbreak may ultimately be its timeline.

The May 15 declaration marked the moment the outbreak became visible to authorities. It did not necessarily mark the beginning of transmission.

Weeks may already have been lost.

The February funeral under investigation, the April death of the nurse, subsequent infections among healthcare workers and the eventual confirmation of Bundibugyo virus form part of a chronology that investigators are still piecing together.

For Kenya and other countries watching the outbreak from outside DRC, the lesson is straightforward.

The first confirmed case is not necessarily the first infection.
The first laboratory result is not necessarily the beginning.

And an official outbreak declaration can come only after a virus has already been moving through people.

The real test of preparedness, therefore, is not how quickly a country responds after Ebola is confirmed.

It is how quickly its health system recognises that something unusual is happening before the virus gets the chance to move ahead of it.