Origins of a 2021 Ebola virus outbreak

A new outbreak of Ebola virus disease in Guinea was declared in February 2021. The country had been free from Ebola virus since the end of the 2013–2016 outbreak in West Africa. The probable index case fell ill and died in January 2021; in the week following her death, several family members attending her funeral became ill and were diagnosed with Ebola virus disease. Alpha Keita and colleagues sequenced viral genomes from 14 confirmed cases and found that the 2021 viral lineage is nested within a clade that predominantly consists of genomes sampled from Guinea in 2014. Furthermore, the 2021 cluster showed far fewer substitutions than would be expected during 6 years of evolution during sustained human-to-human transmission. The finding suggests the possibility that the virus remerged after a long period of latency within a survivor of the previous epidemic. Ebola virus persistence and reactivation has been seen before; this new outbreak suggests that persistence and reactivation may occur over longer time periods and that the long-term monitoring of survivors of Ebola virus disease for the presence of virus in body fluids, or vaccination to boost antibody responses in survivors, might be warranted. The authors emphasize that such work needs to be conducted with the utmost care for the well-being of survivors, who already experience different forms of stigmatization.