Rapid Geographic Expansion, Decelerating Growth, and Six-Month Scenario Projections of Bundibugyo Virus Disease in the Democratic Republic of the Congo: Analysis of Situation Reports 1–61

In May 2026, the Democratic Republic of the Congo declared an outbreak of Bundibugyo virus disease caused by Bundibugyo ebolavirus. We analysed aggregated official Situation Reports (SitReps) issued from 14 May through 14 July 2026 to describe the reported epidemic trajectory, geographic expansion, mortality, interval-specific growth, and conditional six-month projections. Confirmed cases increased from 8 to 2073 and confirmed deaths reached 796; 45 health zones in five provinces were affected. Average interval-specific growth rates generally declined over the observation period, although cumulative cases and the geographic footprint continued to increase. Gompertz and Richards curves described the observed cumulative trajectory better than logistic and exponential curves according to root mean square error (RMSE), the corrected Akaike information criterion (AICc), and the Bayesian information criterion (BIC); this comparison reflects in-sample fit only. Conditional six-month scenarios varied substantially across assumptions (approximately 2435 to 10,839 cumulative cases by 14 January 2027) and are contingent and highly uncertain; Gompertz fits showed underprediction of the subsequently reported total in four temporal checks. Reported case fatality ratios (CFRs) varied across provinces but are vulnerable to outcome delay, incomplete case ascertainment, small denominators, and retrospective reclassification. The results support continued surveillance and response planning but do not identify the causes of epidemic slowing or establish that transmission was controlled.