An Ebola outbreak in Guinea that has so far sickened at least 18 people and killed nine has stirred difficult memories of the devastating epidemic that struck the West African country between 2013 and 2016, along with neighboring Liberia and Sierra Leone, leaving more than 11,000 people dead.

But it may not just be the trauma that has persisted. The virus causing the new outbreak barely differs from the strain seen 5 to 6 years ago, genomic analyses by three independent research groups have shown, suggesting the virus lay dormant in a survivor of the epidemic all that time. “This is pretty shocking,” says virologist Angela Rasmussen of Georgetown University. “Ebolaviruses aren’t herpesviruses”—which are known to cause long-lasting infections—“and generally RNA viruses don’t just hang around not replicating at all.” //

The Guinea Center for Research and Training in Infectious Diseases (CERFIG) and the country’s National Hemorrhagic Fever Laboratory have each read viral genomes from four patients; researchers at the Pasteur Institute in Dakar, Senegal, sequenced two genomes. In three postings today on the website virological.org, the groups agree the outbreak was caused by the Makona strain of a species called Zaire ebolavirus, just like the past epidemic. A phylogenetic tree shows the new virus falls between virus samples from the 2013–16 epidemic. //

Another ongoing outbreak of Ebola in North Kivu, in the Democratic Republic of the Congo, was also started by transmission from someone infected during a previous outbreak, Delaporte notes. (The survivor had tested negative for Ebola twice after his illness in 2020.) Taken together, that suggests humans are now as likely to be the source of a new outbreak of Ebola as wildlife, he says. “This is clearly a new paradigm for how these outbreaks start.” Outbreaks sparked by survivors may even become more likely, now that increasing mobility and other factors have caused each eruption of Ebola to become bigger, resulting in more survivors, says Fabian Leendertz, a wildlife veterinarian who was involved in the sequencing.