A growing outbreak of the rare Bundibugyo virus in the Democratic Republic of Congo highlights the need for better planning against lesser-known but potentially deadly infectious diseases, according to a review article by Boston University professor Nancy Sullivan published June 24 in the New England Journal of Medicine.

Bundibugyo is a relatively rare virus in the same filovirus family as the better-known Ebola virus. It has caused only two previously recognized disease outbreaks—in Uganda in 2007 and the Democratic Republic of Congo (DRC) in 2012—but the current outbreak has already exceeded the other outbreaks in trajectory and scale. According to the WHO, as of June 11, a total of 695 confirmed cases and 138 confirmed deaths have been reported in the DRC and Uganda.

Sullivan, professor of biology and virology, immunology & microbiology at Boston University, writes that controlling outbreaks requires rapid diagnosis, isolation of infected patients, contact tracing, infection-control measures, and supportive care. However, limited laboratory capacity and delayed testing in resource-constrained settings can slow response efforts and allow transmission to spread.

Bundibugyo causes severe hemorrhagic fever, including systemic inflammation, dysfunction and failure of the lining of blood vessels, uncontrolled bleeding and multiorgan failure. Because it is contracted by direct contact with infected bodily fluids, it can be spread by caregivers, especially in a hospital setting. The 2026 outbreak was officially recognized following the death of a nurse.

The outbreak exposes a weakness in diagnosis, Sullivan said. Because symptoms closely resemble those of malaria, typhoid fever and other diseases, lab testing is required for diagnosis. But limited laboratory capacity in the DRC requires significant travel to national reference laboratories, Sullivan found.

“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.

The outbreak also exposes a weakness in preparedness programs that focus primarily on the most common high-risk pathogens. Despite decades of relative inactivity, Bundibugyo has emerged as a significant threat, underscoring the difficulty of predicting which pathogens will cause the next outbreak. Sullivan has advocated for developing countermeasures to address any pathogen that has the capacity to cause severe disease or death in humans.

Although progress has been made in developing medical countermeasures against the Ebola, Sudan and Marburg viruses, Bundibugyo virus occurs far less frequently and no licensed vaccines or therapeutics specifically targeting it have been developed. But evidence suggests vaccines targeting other virus species may provide some protection.

“Preparedness planning should extend beyond diagnostics, vaccines, and therapeutics to include operational readiness for multinational outbreak response,” she said.