Update (June 21): The World Health Organization announced that the Ebola outbreak in Guinea is over as of June 19. Twelve people have died since the disease emerged there in February this year.
Viral genetic sequences from current Ebola cases in Guinea and from the 2014–2016 West African outbreak are almost identical, according to recent analyses, indicating that the new outbreak was triggered by someone who harbored the virus for five years or more, The New York Times reports.
Ebola cases were identified in Guinea in late January, and the country declared an outbreak on February 13. In total, 18 people have tested positive for the virus and nine people have died.
The Ebola virus can linger in the body long after a person recovers, sometimes triggering or spreading the disease if it reactivates, but about 500 days had been the longest interval on record. Given the length of time since the previous West African Ebola crisis that killed more than 11,000 people, researchers had thought that the new outbreak originated in animals, according to STAT.
Three independent research groups sequenced and compared Ebola virus genomes from the current and 2013–2016 outbreaks. In findings posted to virological.org, a discussion forum for molecular evolution and epidemiology of viruses, one analysis states that the fact that the samples shared several mutations “makes it unlikely that the new cases are a result of a new spillover from the animal reservoir, but instead are directly linked to human cases in the 2013–2016 West Africa EVD [Ebola virus disease] outbreak.” The other two analyses arrive at similar conclusions.
“I was completely shocked,” Angela Rasmussen, a virologist at the Georgetown Center for Global Health Science and Security, tells STAT, in response to the findings.
“To have a new outbreak start from latent infection 5 years after the end of an epidemic is scary and new,” Eric Delaporte, an infectious disease physician at the University of Montpellier who is a member of one of the three teams that performed the genetic analyses, tells Science.
A separate Ebola outbreak was recently declared in Democratic Republic of Congo.