What to know about the new Ebola outbreak that quietly raged for weeks

A rare strain of Ebola has prompted the World Health Organisation to declare a public health emergency of international concern. Most of the cases have occurred in the Democratic Republic of Congo, with more than 100 suspected deaths and nearly 400 suspected infections.

There are concerns over delays to the emergency declaration, with suggestions that the Bundibugyo strain had already been circulating for weeks because health officials were testing for the wrong type of Ebola.

Citing the threat of the outbreak, the Trump administration invoked an emergency public health rule on Monday to seal American borders to those who have recently been in Congo, Uganda or South Sudan.

An American missionary doctor has tested positive for Ebola and has been sent to Germany for treatment along with six others who may have been exposed, the Centres for Disease Control and Prevention said on Monday (US time).

Serge Global, a Christian missionary organisation, said on its website on Monday that Dr Peter Stafford was exposed to Ebola while treating patients at the Nyankunde Hospital in DR Congo. Two physicians with his group – including his wife – remain asymptomatic.

Here is what we know about the outbreak so far:

What is Bundibugyo Ebola?

The current Ebola outbreak – so far limited to the DR Congo and Uganda – is due to a rare strain of the virus known as Bundibugyo, named after Uganda’s Bundibugyo Province, where it was first identified during an outbreak in 2007–2008.

A second Bundibugyo outbreak occurred in 2012 in the DR Congo. Bundibugyo kills 30 to 40 per cent of infected people, making it less lethal than the more common Zaire strain, which causes death in up to 90 per cent, according to a global study published in 2024.

Bundibugyo is one of the four species of Ebolavirus genus that cause life-threatening illness in humans. All Ebola viruses are transmitted through direct contact with the bodily fluids of infected animals or humans or objects contaminated with such fluids.

Body fluid transmission is a particular risk for hospital workers. An American doctor working in DR Congo has been infected in the current outbreak.

According to the World Health Organisation, Ebolaviruses initially cause flu-like symptoms, including fever, fatigue, malaise, muscle pain, headache, and sore throat, that can start suddenly, followed by vomiting and diarrhoea, and eventually by internal and external bleeding and multi-organ failure.

Are there treatments for Bundibugyo?

There are no approved vaccines or drugs for Bundibugyo Ebolavirus. Emergency use authorisation would be necessary for the deployment of any experimental treatments or existing treatments that have been effective against other strains.

Potential candidates that have helped to control Bundibugyo in trials in non-human primates include Merck’s Ervebo, Mapp Biopharmaceutical’s MBP 134, and Auro Vaccines’ VesiculoVax.

NanoViricides said its experimental antiviral drug NV-387, currently in clinical trials against mpox, could be effective against the Bundibugyo strain. It mimics the immune cell surface proteins to which all ebolaviruses attach themselves and could thereby act as a decoy to “soak up” the virus and prevent it from attaching to healthy cells.

Earlier in the pipeline, an mRNA vaccine being developed in China has shown promise against Bundibugyo in mice but has not yet been tested in primates.

For now, response efforts will rely on public health measures such as rapid case detection, isolation, contact tracing, infection prevention and control, safe burials, and community engagement, said Dr Daniela Manno of the London School of Hygiene & Tropical Medicine in a statement.

“These measures were critical in eventually controlling the 2014–2016 West Africa Ebola epidemic, the largest Ebola outbreak ever recorded, and if implemented rapidly and effectively, they can also help control this outbreak,” Manno said.

Is there a test for Bundibugyo?

Tests for Bundibugyo exist but are not widely used. Initial analysis of samples in the current outbreak, using standard tests, did not detect the infections.

“Because early tests looked for the wrong strain of Ebola, we got false negatives and lost weeks of response time,” Dr Matthew Kavanagh, director of the Georgetown University Centre for Global Health Policy & Politics in Washington, said in a statement.

“By the time the alarm was raised, the virus had already moved along major transport routes and crossed borders,” Kavanagh said.

He criticised the Trump administration’s earlier decision to withdraw from the WHO and make deep cuts in foreign aid – “the exact surveillance system meant to catch these viruses early”.

What makes Bundibugyo different from other strains?

Differences in genetic make-up between Bundibugyo and other Ebolaviruses affect its virulence (infectiousness), diagnosis, and the availability of medical treatments.

Compared with the Zaire strain, which replicates rapidly to reach high levels in the patient’s body, the Bundibugyo strain replicates more slowly.

Bundibugyo is also slower to invade, disable and kill immune cells, eventually crippling the patient’s immune defences.

The incubation periods for the Bundibugyo virus and the Zaire virus are nearly identical, however, averaging 8 to 10 days but sometimes lasting up to three weeks.

A recent study of survivors of the 2007 Bundibugyo outbreak found persistent symptoms and immune and metabolic alterations; nevertheless, it concluded that overall, Bundibugyo may have less severe long-term effects on the liver and kidneys than the Zaire strain.

Reuters, AP

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