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Scientists comment on genome sequencing of the Bundibugyo virus in the Democratic Republic of the Congo and Uganda.
Prof David Matthews, Professor of Virology, University of Bristol, said:
“This is a valuable rapid insight into the current outbreak, and it supports the initial finding that Bundibugyo virus is the cause. This is important because Bundibugyo virus disease has only caused two known outbreaks before, one in Uganda in 2007 and in 2012 in DRC. The Virological analysis reports that the initial genomes are consistent with a new spillover event by a Bundibugyo ebolavirus that is similar but distinct from these previous outbreaks.
“Genomic sequencing is valuable because it helps establish whether the outbreak is likely to have arisen from a single spillover event, followed by human-to-human transmission, or whether there may have been multiple separate introductions from an animal reservoir. The current dataset is still very preliminary, but so far it appears most consistent with a single recent introduction followed by onward person to person spread. That is useful because it suggests this outbreak can potentially be traced and interrupted as it has been in the past. Repeated independent spillovers from an animal source would complicate the efforts to stop the outbreak.
“Confirming this is not Zaire ebolavirus also has practical consequences: the licensed Ebola vaccine most often used in recent outbreaks is matched to Zaire ebolavirus and should not be assumed to protect well against Bundibugyo virus. This reinforces the need to speed up work on Bundibugyo-specific vaccines and other countermeasures.
“Further sequencing will also help make sure that any vaccine or antibody-based countermeasure in development will be closely matched to the virus causing this outbreak. As such it will be important to monitor the current outbreak virus directly rather than relying only on older reference sequences.
“Finally, genomic data can help work out how the virus is spreading. For example, if viruses found in different patients or locations are very similar or identical, that supports a recent link between the two individuals which can help investigators identify transmission chains that may otherwise be missed. In this way, sequencing complements contact tracing and can help inform public health advice that helps people to understand how to limit the spread of the virus. So, it can help confirm whether the usual Ebola control measures are successful or need adapting. With more data from more patients over time it can also help epidemiologists work out when the likely spillover event first occurred.
“We saw the value of this kind of rapid sequencing during the COVID-19 pandemic, where sequencing was used to track the emergence and spread of new variants and to monitor whether vaccines, diagnostics or treatments might need updating.”
Dr Charlotte Houldcroft, Assistant Professor of Virus Genomics, University of Cambridge, said:
Why is it important to sequence the genomes of the samples?
“Having genome sequences available from the emerging Bundibugyo virus outbreak is vital to help us develop rapid diagnostic tests specific to this type of Ebola. Genome sequences will already be informing vaccine work, as vaccine candidates for Bundibugyo virus have been tested in animals in the past, but we need to know if those vaccines are still a good match to the current outbreak strain.
What information can it tell us and how can it help in combating the outbreak?
“Genome sequences were really powerful in the 2014-2016 West African Ebola outbreak: they helped public health teams track, and most importantly break, transmission chains. Genome sequences were also useful for understanding very rare cases of survivors who may harbour persistent Ebola virus which is not cleared from the body and that can kick off new chains of transmission. We also want to identify, if possible, where this Bundibugyo virus outbreak originated: did it come directly from a wild animal, or has the outbreak been smouldering in humans for longer than currently realised?
Is there anything that we can see in this data that is novel or unusual in the genomes?
“Currently we have three new genomes, and they are broadly similar to the two previously known outbreaks (2007, 2012) but not direct descendants of either. This is consistent with the current Bundibugyo virus outbreak coming from an animal reservoir into humans – sometimes known as a spillover event; but we will likely need more genetic and epidemiological data to know how long this outbreak has been transmitting human to human.”
Prof Miles Carroll, Professor of Emerging Viruses, Pandemic Sciences Institute, University of Oxford, said:
“Using a method termed “molecular epidemiology”, rapid sample genome sequencing can enable scientists to understand who has infected who, as each sample will have a unique genetic signature. The relationship of these genetic signatures can help public health responders understand how the virus is spreading and lead to the shutdown of chains of transmission.
“Understanding how the virus is evolving is also important to ensure the current diagnostics will continue to be effective.
“It is essential that colleagues in DRC are provided with the essential scientific supplies to enable them to sequence rapidly and broadly to support molecular epidemiology. I imagine the initial target will be to sequence 500 samples ASAP.”
* Initial genomes from May 2026 Bundibugyo Virus Disease Outbreak in the Democratic Republic of the Congo and Uganda
Declared interests
Dr Charlotte Houldcroft: Charlotte Houldcroft’s group hosts a PhD student part-funded by Virothera, an immune therapeutics developer.
Prof Miles Carroll: No COI
For all other experts, no reply to our request for DOIs was received.