select search filters
briefings
roundups & rapid reactions
Fiona fox's blog
Scientists comment on an Ebola outbreak in the Democratic Republic of Congo (DRC).
Dr Anne Cori (and team*), Associate Professor in Infectious Disease Modelling, School of Public Health – Faculty of Medicine, Imperial College London, said:
What is Ebola, how is it spread, what are the symptoms and how is it treated?
“Ebola virus disease (EVD) is a viral haemorrhagic fever caused by species of orthoebolaviruses (here referred to as EBOV). EVD has caused over 40 documented confirmed outbreaks since 1976 [https://www.cdc.gov/ebola/outbreaks/index.html], with an average case fatality ratio over 50% [https://pubmed.ncbi.nlm.nih.gov/39127058/]. Outbreaks are typically linked to zoonotic spillover (animal-to-human transmission) followed by human-to-human transmission via close contact with an infected individual’s bodily fluids (either directly or through shared bedding/other surfaces).
“There are four distinct species of orthoebolavirus known to affect humans: Zaire, Sudan, Bundibugyo and Tai Forest. Zaire is the most well-documented due to its involvement in major outbreaks (e.g. the 2013-16 West African EVD outbreak). The Sudan species has caused nine outbreaks since 1976, most recently in January 2025. Bundibugyo has only caused two outbreaks in 2007 and 2012, and Tai Forest is only known to have infected a single person in Cote d’Ivoire in 1994 [https://www.cdc.gov/ebola/outbreaks/index.html]. As a result, the epidemiology of the non-Zaire species, particularly the Bundibugyo and Tai Forest species, is not as well characterised [https://pubmed.ncbi.nlm.nih.gov/39127058/].
“The symptoms of Ebola infection can be sudden and include fever, fatigue, muscle pain, headache and sore throat followed by vomiting, diarrhoea, rash, and internal and external bleeding. Treatment options are limited: only two monoclonal antibody (mAb) therapeutics are licensed for use, and both are specific to Zaire, with none available for other EBOV species [https://www.who.int/news-room/fact-sheets/detail/ebola-disease]. Without therapeutic options, treatment is limited to supportive care, such as rehydration and the stabilisation of oxygen and blood pressure.
What do we know so far about this outbreak? What strain is causing the outbreak?
“As of 15th May 2026, Africa CDC has reported 246 suspected cases (i.e. individuals with symptoms compatible with Ebola but who have not been confirmed by laboratory testing), and 65 deaths, mainly in Mongwalu and Rwampara health zones in North Eastern DRC, not far from the Ugandan border [https://africacdc.org/news-item/africa-cdc-calls-for-urgent-regional-coordination-meeting-following-ebola-virus-disease-outbreak-in-ituri-province-drc/]. Of those suspected cases, 13 were confirmed by diagnostic testing, of whom 4 died.
“Genomic analyses are underway to confirm the species causing the outbreak with results expected in the next 24 hours. The initial Africa CDC report mentions that the results of 20 samples tested (of which 13 were positive for Ebola) suggest this is not the Zaire species.
How is an outbreak of Ebola contained? What are the challenges here?
“Non-pharmaceutical interventions are cornerstones of Ebola outbreak response. These interventions include active case finding and isolation, contact tracing, and safe burials, as Ebola is very deadly (about half of infected people die) and particularly infectious around the time of death [https://www.afro.who.int/publications/regional-strategic-preparedness-and-response-plan-ebola-virus-disease-outbreak].
“Deploying these non-pharmaceutical interventions is feasible in theory, but can become very resource-intensive and challenging as soon as case numbers are large, and especially in large urban centres, highly connected areas, or areas impacted by conflict. Additionally, late detection of an outbreak can have catastrophic consequences (e.g. in West Africa [https://www.nejm.org/doi/full/10.1056/NEJMsr1513109]).
“A global stockpile of a licensed Ebola vaccine exists and can be delivered in response to an outbreak (by vaccinating contacts of cases or individuals living in an affected area) [https://www.who.int/groups/icg/ebola-virus-disease/ebola-stockpiles], but this only protects from infection with Ebola Zaire (the species which historically has caused most and the largest outbreaks). There are currently no vaccines licensed for other species.
“So if it is confirmed there have already been 246 cases and 65 deaths, this would suggest ongoing transmission has occurred for several weeks, and the outbreak has been detected very late, which is concerning. In addition, if it is confirmed that this is not the Zaire species, this could be potentially challenging to control in the absence of a vaccine.
“Additional challenges specific to this outbreak include high mobility and connectivity in this region and conflicts which have historically made Ebola responses more challenging [https://www.sciencedirect.com/science/article/pii/S2590088920300020?via%3Dihub][https://www.nejm.org/doi/full/10.1056/NEJMsr1904253].
Is this a significant outbreak compared to previous outbreaks?
“To date, there have been 33 documented zoonotic spillover events involving Ebola viruses (excluding laboratory-related transmission), 25 of which were caused by the Zaire species [https://www.cdc.gov/ebola/outbreaks/index.html].
“If the current outbreak size is confirmed at 246 cases, it would rank as the 7th largest outbreak across all species. If the causative virus is not the Zaire species, it would represent the second largest non-Zaire outbreak on record. By comparison, the largest recorded Sudan virus disease outbreak occurred in Uganda in 2000, with 425 reported cases and 224 deaths.
“This is particularly significant because it suggests an unusually high number of suspected cases were identified before the outbreak was officially declared. This indicates that the outbreak has likely gone undetected for several weeks or even months, which can make standard control measures, such as contact tracing, considerably more difficult to implement effectively, especially in a setting which already faces other challenges such as conflict.
Is there risk to the rest of DRC or other nearby countries?
“Yes, as stated by the African CDC in their press release on 15 May 2026 [https://africacdc.org/news-item/africa-cdc-calls-for-urgent-regional-coordination-meeting-following-ebola-virus-disease-outbreak-in-ituri-province-drc/], there is risk to both the rest of the DRC and nearby countries of Uganda and South Sudan due to their geographical proximity and high connectivity within the affected regions. Bunia and Rwampara are urban centres associated with high population movement, while Mongwalu is a mining town potentially well connected to the rest of the country. The region is highly unstable due to ongoing conflict which makes outbreak detection and response challenging.
Is there any risk to the UK?
“The risk to the UK is very low; in the 2013-16 West African Ebola outbreak there were only a handful of cases exported to Europe despite almost 30,000 cases, and these were mostly international healthcare workers repatriated after being infected. There is no documented sustained spread of Ebola outside of Africa (no more than 1-2 generations of infection and mostly among healthcare workers).
Any other comments?
“There is limited official information released at the moment. The evidence emerging in the next few days, including the characterisation of the species (expected in the next day or so) will be critical to better understand the epidemiological risk associated with this event.
“But if the case number is confirmed to be 246 cases and if the species is confirmed to not be Zaire, this would suggest transmission has been ongoing for a while, and it would already make this outbreak the second largest ever for a non-Zaire Ebola species. In the context of an urban and well-connected area, and in the absence of a vaccine for that species, this would be concerning news.”
*colleagues Dr Gemma Nedjati Gilani, Dr Ruth McCabe, Dr Rebecca Nash, Dr Janetta Skarp, Dr Christian Morgenstern, Dr Sabine van Elsland also helped with writing this comment
Dr Daniela Manno, Clinical Assistant Professor at the London School of Hygiene & Tropical Medicine (LSHTM), said:
What is Ebola, how is it spread, what are the symptoms and how is it treated?
“Ebola virus disease is a severe infection caused by viruses of the genus Orthoebolavirus. The virus spreads through direct contact with blood, bodily fluids, or contaminated materials from an infected person, particularly during the later stages of illness. Early symptoms include fever, fatigue, headache, muscle pain, sore throat, vomiting and diarrhoea, while severe disease can progress to bleeding complications, multi-organ failure, and death.
“While Ebola remains a serious disease, outbreak prevention, response, and treatment have improved significantly over the past decade. Rapid identification and isolation of cases, contact tracing, infection prevention and control measures, and safe burials are all important components of outbreak control.
“There are now vaccines available for some viruses causing Ebola disease, which can help protect healthcare workers and reduce transmission when deployed rapidly around confirmed cases and their contacts in a strategy known as ring vaccination. Early diagnosis can also allow prompt supportive care, including fluid resuscitation, pain management, and treatment of complications. In addition, specific therapeutics are now available for some Ebola viruses and can substantially reduce mortality when given early.
What do we know so far about this outbreak? What strain is causing the outbreak?
“Based on currently available information, sequencing and laboratory investigations are still ongoing. Africa CDC has indicated that initial findings may suggest a virus different from Ebola virus, although this has not yet been fully characterised. This will be important to clarify because available vaccines and therapeutics differ depending on the virus involved. For example, vaccines and therapeutics currently available for Ebola virus may not provide the same protection against other Ebola-causing viruses such as Sudan virus.
“At present, there also remains an important distinction between suspected and laboratory-confirmed cases. Additional laboratory confirmation and epidemiological investigations will be essential to better understand the scale, transmission dynamics, and origin of the outbreak.
Is there risk to the rest of DRC or other nearby countries?
“The outbreak is occurring in Ituri province, an area of DRC affected by insecurity, population displacement, limited infrastructure, and highly mobile communities linked to mining activities. These factors can make Ebola outbreaks particularly difficult to contain because they complicate surveillance, contact tracing, delivery of healthcare, vaccination campaigns, and safe transport of samples and patients. Cross-border coordination with neighbouring countries will also be important given the high population mobility in the region.
“At the same time, DRC has extensive experience responding to Ebola outbreaks and response capacity is significantly stronger today than it was a decade ago. The country has established laboratory networks, trained outbreak response teams, vaccination strategies, and international partnerships that can be rapidly mobilised.
Is there any risk to the UK?
“Although this is a serious outbreak that requires urgent public health action, there is currently no evidence that it poses a significant risk to the UK public. Ebola does not spread through the air in the same way as respiratory viruses such as influenza or COVID-19, and transmission generally requires direct contact with bodily fluids or contaminated materials from an infected person. The main risks remain within affected communities and among healthcare workers or caregivers in close contact with infected individuals.
Any other comments?
“More broadly, recurrent Ebola outbreaks highlight the importance of sustained investment in surveillance, outbreak preparedness, strong health systems, and understanding the environmental and social drivers of spillover events at the human–animal interface.”
Dr Amanda Rojek, Associate Professor of Health Emergencies, Pandemic Sciences Institute, University of Oxford, said:
What is Ebola, how is it spread, what are the symptoms, and how is it treated?
“Ebola belongs to a group of diseases called viral haemorrhagic fevers. It spreads through direct contact with the blood or other body fluids of a person who is sick with Ebola, or through contact with contaminated materials. It is not airborne. Common symptoms include fever, fatigue, headache, vomiting, diarrhoea, and, in some cases, bleeding.
“Treatment is best when started early and focuses on supportive care such as rehydration and management of complications. For Ebola virus disease caused by Zaire ebolavirus (which seems to not be the cause for this outbreak), there are licensed monoclonal antibodies for treatment. At the moment, there are no licensed treatments for other strains, and so promising treatments should be evaluated in a clinical trial.
What do we know so far about this outbreak? What strain is causing the outbreak?
“What we know so far is that this is a potentially serious outbreak in Ituri province. DRC is a country experienced in managing Ebola outbreaks. Africa CDC says there are 246 suspected cases and 65 deaths at this stage, with laboratory tests confirming Ebola virus in 13 of 20 samples. Preliminary reports are that this outbreak is caused by a non-Zaire ebolavirus (with Zaire being the most commonly encountered strain). We will need to wait for further confirmation to understand which other strain is causing the outbreak – in recent years there have been outbreaks of two closely related viruses (Marburg, and Sudan), but given the location, other strains might also be possible. This will have implications particularly for the severity of patient illnesses, but we’ll need to know which strain is responsible before understanding these ramifications.
How is an outbreak of Ebola contained? What are the challenges here?
“Containment depends on rapid case finding, access to treatment, contact tracing for 21 days, safe burials, PPE for health workers, and community engagement. The location matters – poor infrastructure and high population movement might make containment more challenging. On the other hand – the DRC is a country experienced in managing these outbreaks.
Is this a significant outbreak compared to previous outbreaks?
“Compared with recent outbreaks, the current outbreak already appears significant because the reported case and death counts are high. That being said, reported suspected cases are not directly comparable with confirmed/probable totals from prior outbreaks, so I would avoid drawing firm conclusions about severity until surveillance and sequencing are clearer.”
Prof Paul Hunter, Professor in Medicine, UEA, said:
“Ituri Province has had previous outbreaks of Ebola. It is also a place where there is a vicious conflict with civilians being targeted (https://www.globalr2p.org/publications/atrocity-alert-no-482/) even in recent weeks.
“This makes control difficult as vaccine workers have been murdered during previous outbreaks and vaccine is the primary method of controlling an outbreak like this. The conflict would also likely have delayed recognition of the outbreak again contributing to delayed intervention and ongoing spread
“All Ebola outbreaks start with an animal to human transmission event, usually fruit bats. The infection then spreads person-to-person until it is controlled. Essentially transmission is usually through close physical contact with a sick person. So caring for a sick patient (this is why health care workers are often affected) and sharing beds are high risk. One of the big accelerators are funerals as people come into close contact with the deceased in some cultures.”
Declared interests
Dr Daniela Manno: Dr Daniela Manno has previously worked on Ebola vaccine clinical trials and outbreak preparedness research in Sierra Leone, Tanzania, and the Democratic Republic of Congo.
Dr Amanda Rojek: I’m the clinical lead for the WHO sponsored PARTNERS trial (the treatment trial in the region).
Prof Paul Hunter: “No COIs.”