A rare strain of Ebola that began spreading undetected in eastern Democratic Republic of Congo (DRC) in early April 2026 is now confirmed to be infected in Uganda and could reach South Sudan, according to a new modeling study published by the World Health Organization (WHO). lancet infection journal.
The current outbreak caused by the Bundibugyo Ebola virus was officially declared on May 15, 2026. As of June 22, 2026, 1,048 laboratory-confirmed cases and 267 confirmed deaths have been recorded across the affected health areas of the DRC. The initial number of suspected cases peaked at 1,077 on May 26, 2026, but was revised downward after laboratory tests confirmed that many of these patients had other illnesses rather than Ebola. On May 17, 2026, WHO declared a Public Health Emergency of International Concern (PHEIC), the highest level of international health alert. According to the study, retrospective investigation shows that the infection began in early April 2026. The six-week delay between the presumed first case and official confirmation suggests that the virus was spreading undetected through communities in the region, already destabilized by conflict, displacement and limited access to health care.
Bundibugyo Ebola virus is one of several strains of the Ebola virus. The virus was first identified during an outbreak in western Uganda in 2007, and caused a second outbreak in the Democratic Republic of Congo in 2012. Compared to the more familiar Zaire strain, which caused an outbreak in West Africa from 2014 to 2016, the Bundibugyo strain tends to be slightly less deadly and less transmissible. However, it still causes severe hemorrhagic fever, kills a significant proportion of those infected, and is spread by direct contact with the body fluids of sick or deceased people.
There is no licensed vaccine specifically for the Bundibugyo Ebola virus, and prevention and control measures such as isolation of infected individuals, contact tracing, and safe burial practices are essential public health measures to stop the spread of the disease. The authors say these measures are particularly important given the congested border crossings between the Democratic Republic of the Congo and neighboring countries such as Uganda and South Sudan.
Researchers used computer models to simulate how an outbreak would spread under three different scenarios: low infectivity, central (most likely), and high infectivity. The study projects that under the most likely (central) scenario, the cumulative number of confirmed cases would reach around 990 and 174 deaths by late June 2026, and around 8,210 by September 2026 if infections simply persist. As of June 15, 2026, 837 confirmed cases have been recorded, consistent with the central scenario. Under the low-case scenario, around 870 people will be infected and around 160 people will die by late June. In the worst-case scenario, if containment measures fail, it predicts the number of infections could exceed 66,000 by September. However, the authors note that the rate of new cases in recent weeks suggests the outbreak is more likely to follow the low-to-moderate end of these projections than the worst-case scenario.
As of June 22, 2026, there have been 20 confirmed cases of Ebola hemorrhagic fever and two deaths in Uganda, including five confirmed cases among healthcare workers. Some of these cases were brought across the border from the DRC, while others were captured locally from these individuals. Uganda was able to quickly identify and respond to cases, drawing on its experience in managing past Ebola outbreaks and the public health system it had built over many years.
Researchers have now identified South Sudan as the most urgent priority for preparedness, estimating that there is a nearly seven-in-ten (69.3%) chance that at least one infected person will arrive in South Sudan within the 12-week modeling timeline. South Sudan also has some of the weakest public health infrastructure in the region, with known deficiencies in case management, contact tracing, safe burials, and border surveillance. Rwanda (8.6%) and Burundi (2.0%) remain at relatively low risk. However, the study authors note that the risk could still increase, depending on detection capabilities, travel patterns, and the speed of each country’s response system.
The authors note that this study has several limitations. This projection is based on a mathematical model that is adjusted based on the latest number of confirmed cases, so if that number changes as more test results become available, the projection may change accordingly. The model also treats the affected population as homogeneous and cannot fully account for differences between regions in terms of geography, access, or how effective local control measures are working. Estimates of how many people cross the border unofficially each day are also uncertain. The authors emphasize that these findings should be treated as an early assessment of the situation, aimed at facilitating advance preparedness, rather than precise predictions, and that predictions will be updated as more validated data becomes available.
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Reference magazines:
Chamla, D. Others. (2026). The scale of the 2026 Ebola outbreak and its implications for cross-border spillover risks and preparedness from Bundibugyo virus in Ituri province, Democratic Republic of the Congo: A recalibrated stochastic modeling study. lancet infection. DOI: 10.1016/S1473-3099(26)00320-8. https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(26)00320-8/fulltext
