A growing outbreak of the rare Bundibugyo virus in the Democratic Republic of Congo is drawing attention to a broader problem in global health: how to prepare for dangerous diseases that appear only rarely but can still cause deadly outbreaks.
In a review article published in the New England Journal of Medicine, Boston University professor Nancy Sullivan argues that outbreak preparedness needs to extend beyond the infectious diseases that receive the most attention.
A Rare Relative of Ebola
Bundibugyo belongs to the filovirus family, the same group of viruses that includes the much better-known Ebola virus. Despite its potential severity, Bundibugyo has been linked to only two previously recognized outbreaks, one in Uganda in 2007 and another in the Democratic Republic of Congo (DRC) in 2012.
The current outbreak, however, has already surpassed those earlier events in both its trajectory and scale. According to the WHO, 695 confirmed cases and 138 confirmed deaths had been reported in the DRC and Uganda as of June 11.
Sullivan, a professor of biology and virology, immunology & microbiology at Boston University, explains that bringing an outbreak under control depends on several measures working quickly together. These include rapid diagnosis, isolating infected patients, tracing people who may have been exposed, strengthening infection control, and providing supportive medical care.
Those steps become much harder when laboratory resources are limited. In settings where testing capacity is scarce, delays in confirming infections can give the virus more time to spread.
A Severe Hemorrhagic Fever
Bundibugyo can cause a severe form of hemorrhagic fever. Infection can trigger widespread inflammation, damage and failure of the cells lining blood vessels, uncontrolled bleeding, and failure of multiple organs.
The virus spreads through direct contact with infected bodily fluids. That creates particular risks for family members, caregivers, and health workers, especially when patients are being treated in hospitals without adequate infection control. The 2026 outbreak was formally recognized after the death of a nurse.
Another major challenge is that Bundibugyo can initially resemble several far more common illnesses. Symptoms overlap with malaria, typhoid fever, and other diseases, meaning laboratory testing is necessary to confirm an infection.
Testing Delays Can Slow the Response
Laboratory access remains limited in parts of the DRC, Sullivan found, and samples may need to travel considerable distances to reach national reference laboratories. That can turn a critical diagnosis into a lengthy process.
"Delays in specimen collection, transportation and testing can postpone confirmation by days or weeks, which hinders the isolation of infected persons, contact tracing and the initiation of outbreak-control measures," Sullivan wrote.
Those delays can be especially damaging during an outbreak, when identifying cases quickly is essential for separating infected people from others and finding anyone who may have been exposed.
The Risk of Overlooking Rare Viruses
The Bundibugyo outbreak also points to a larger weakness in preparedness strategies that concentrate heavily on the most familiar high-risk pathogens.
For decades, Bundibugyo caused relatively little recognized activity. Its return as a significant threat illustrates how difficult it can be to predict which infectious disease will drive the next major outbreak.
Sullivan has argued that medical countermeasures should be developed more broadly for pathogens capable of causing severe illness or death in humans, rather than focusing only on viruses already known to cause frequent outbreaks.
No Licensed Bundibugyo Vaccine
Considerable progress has been made toward vaccines and other medical countermeasures for the Ebola, Sudan and Marburg viruses. Bundibugyo, however, occurs much less often, and no licensed vaccine or therapeutic has been developed specifically to target it.
There are encouraging signs that vaccines designed against other virus species could offer at least some protection, but Bundibugyo remains an example of a dangerous pathogen for which dedicated medical tools are limited.
Sullivan says preparedness also needs to involve much more than creating diagnostic tests, vaccines and drugs. Health systems must be capable of coordinating quickly when outbreaks spread across borders.
"Preparedness planning should extend beyond diagnostics, vaccines, and therapeutics to include operational readiness for multinational outbreak response," she said.