ONE CHAIN, REPEATED SPILLOVER, OR AN UNRELATED EARLY SIGNAL?

A study investigated the occurrence of Bundibugyo virus disease (BVD) in the Mongbwalu region of Congo. Researchers found that significant illness and mortality occurred in January and February 2026, several months before BVD was officially recognized in May 2026. Using mathematical models, they compared four hypotheses about the origin of the outbreak: continuous transmission, repeated spillover from animals, transmission from survivors, or unconfirmed early deaths. Results showed that the hypothesis of repeated animal spillover or unrelated early deaths was most frequently supported, with a probability of 84.8 percent. Continuous transmission from January to May was least likely, with a probability of only 9.6 percent. The researchers concluded that the May BVD outbreak probably originated from a new environmental spillover rather than from continuation of the January cases.