A highly lethal and unidentified disease is spreading in the rainforests of Congo, the outbreak is believed to have started in the Congolese village of Boloko, where three young children ate a bat and subsequently passed away. Since then, over 400 cases have been reported, with at least 53 fatalities. Genetic testing in Kinshasa, the capital of the Democratic Republic of Congo, has ruled out Ebola and Marburg as the cause, according to an interim report from the World Health Organization (WHO). Professor Martin Grobusch, head of the Center for Tropical Medicine and Travel Medicine at Amsterdam UMC and a member of the Amsterdam Institute for Immunology and Infectious diseases, shares his insights on the outbreak.

Outbreak and symptoms

The three children who first fell ill died between January 10 and 13. More fatalities followed in Boloko and the nearby village of Danda. Victims displayed symptoms such as fever, vomiting, diarrhea, fatigue, abdominal pain, muscle aches, and headaches. Some also experienced bleeding, similar to hemorrhagic viral diseases like Ebola and Marburg. However, PCR tests conducted at the National Institute of Biomedical Research in Kinshasa ruled out both viruses.

On February 9, Congolese health authorities identified a second outbreak cluster in Bomate, a town 150 kilometers northeast of Boloko. Though researchers found no direct link between the two outbreaks, symptoms were consistent. Bomate reported over 400 cases and at least 45 deaths. Samples from this cluster also tested negative for Ebola and Marburg.

Overwhelmed medical facilities and the remote location of the outbreak have led WHO to warn of a "heightened risk" of further spread. Authorities have yet to determine whether the cause is an infectious disease or a toxic substance. Possible culprits under investigation include malaria, an unidentified viral hemorrhagic fever, food or water poisoning, typhoid, and meningitis.

Risk of global spread?

‘The immediate risk of this disease spreading to Europe is low, as the outbreak is in a remote area with minimal travel to Europe,’ says Professor Grobusch. ‘However, for people in the affected region, this is deeply concerning.’ He notes that poor healthcare infrastructure, poverty, and ongoing armed conflicts make the local population particularly vulnerable.

These challenges also complicate the identification of a known pathogen. ‘In December, another mysterious outbreak occurred in southwest Congo. It was later confirmed as malaria, but coexisting anemia and malnutrition made it appear different from typical cases,’ Prof. Grobusch explains.

Congo frequently experiences outbreaks of unknown diseases. As one of the world’s poorest countries, many residents rely on consuming wild animals, which serve as reservoirs for various pathogens. Bats, in particular, are known to carry numerous viruses.

Could this be a new pathogen?

Initially, Prof. Grobusch was surprised that Ebola and Marburg were ruled out. ‘Given the bat exposure, those would have been my first assumptions. But with multiple outbreak clusters, that became less likely, and PCR tests confirmed their exclusion.’

A new, unidentified pathogen remains a possibility. Remote rainforests, where human-animal interactions are frequent, are known hotspots for emerging diseases. ‘However, common viruses are still more likely than a brand-new disease,’ Prof. Grobusch adds.

Further research is crucial to uncover the source of the outbreak. ‘It is unlikely the three children got sick from something unrelated to the bat, but we still don’t know if the other clusters are directly connected.’

Source: Read the original article (in Dutch) written by Sander Voormolen and Karlijn Saris on the website of NRC.nl.

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