Genomic characterization uncovers transmission dynamics of Marburg Virus in Rwanda following a single zoonotic spillover event

The ongoing outbreak of Marburg virus disease (MVD) in Rwanda marks the third largest historically, though it has exhibited the lowest fatality rate. Genomic analysis has identified a lineage with limited internal diversity most closely related to a genome sequence from a sporadic case sampled in 2014 in Uganda, though the lineages have diverged from a common ancestor that was circulating for decades in the animal reservoir. Notably, the data also provide evidence that the outbreak resulted from a single zoonotic transmission event with limited human-to-human transmission, rather than multiple independent zoonotic transmission events. The Rwandan MVD outbreak prompted a thorough investigation that included contact tracing, clinical assessment, travel history, sequencing, and serology testing, to trace the virus’s origin. Results of investigations linked the index case to a mining cave inhabited by Rousettus aegyptiacus (the Egyptian fruit bat), where three individuals tested seropositive for IgG and IgM, further supporting the zoonotic origin of the outbreak through human-animal interactions.