Investigating the zoonotic origin of the Marburg virus outbreak in Guinea in 2021

In 2021, a patient died from Marburg virus (MARV) disease in Guinea, which was the first confirmed case in West Africa. The source of the outbreak has not been identified. It was revealed only that the patient had not traveled anywhere before the illness. Prior to this outbreak, MARV had been found in bats in the neighboring Sierra Leone. In Guinea, this virus has never been found before. Therefore, the question of the source of infection arose: was it an autochthonous case with spillover from a local population of bats or an imported case with spillover from fruit bats foraging/migrating from Sierra Leone? In this paper, we aimed to conduct a study of Rousettus aegyptiacus in Guinea and determine the source of the most likely infection of a patient who died from Marburg virus disease in 2021 in Guinea. We caught bats at 32 sites in Gueckedou prefecture, including seven caves and 25 locations on the flight path. A total of 501 fruit bats (Pteropodidae) were captured, including 66 R. aegyptiacus. The subsequent screening showed three PCR-positive MARV bats. We have found and described two caves in Gueckedou prefecture where MARV-positive R. aegyptiacus roost. Sequencing has shown that at least two different MARV genetic variants circulate in R. aegyptiacus in Guinea: an Angola-like strain and MARV strains of major marburgvirus lineages.