The Ebola virus can cause latent infections in survivors that can cause new outbreaks.
National Institutes of Allergy and Infectious Diseases / National Institutes of Health / Flickr (CC BY-NC 2.0)
By Kai Kupferschmidt
An Ebola outbreak in Guinea that has killed at least 18 people so far and killed nine has fueled difficult memories of the devastating epidemic that hit the West African country between 2013 and 2016, along with neighboring Liberia and Sierra Leone , and more than 11,000 people died.
But it may not be just the trauma that has continued. The virus causing the new outbreak is hardly different from the strain seen 5 to 6 years ago, genomic analyzes by three independent research groups have shown, suggesting that the virus is constantly in a survivor of the epidemic. “It’s pretty shocking,” says virologist Angela Rasmussen of Georgetown University. “Ebola viruses are not herpes viruses” – which are known to cause long-term infections – “and in general RNA viruses do not just hang around and are not repeated at all.”
Scientists knew that the Ebola virus could persist in the human body for a long time; a revival in Guinea in 2016 arose from a survivor who shed the virus in his semen more than 500 days after his infection and infected a partner through sexual intercourse. “But starting a new outbreak of latent infection five years after the end of an epidemic is scary and new,” said Eric Delaporte, a physician at the University of Montpellier who studied Ebola survivors. and is a member of one of the three teams. Outbreaks of Ebola survivors are still very rare, says Delaporte, but the finding raises difficult questions about how to prevent them without further stigmatizing Ebola survivors.
The current outbreak in Guinea was detected after a 51-year-old nurse who was initially diagnosed with typhus and malaria died at the end of January. Several people who attended her funeral became ill, including members of her family and a traditional healer who treated her, and four of them died. Researchers suspect that Ebola could have caused all the deaths, and in early February, they discovered the virus in the nurse’s husband’s blood. An Ebola outbreak was officially declared on February 13, with the nurse as the possible index case.
The Guinea Center for Infectious Disease Research and Training (CERFIG) and the country’s National Hemorrhagic Fever Laboratory each read viral genomes from four patients; researchers at the Pasteur Institute in Dakar, Senegal, have two genomes in succession. In three posts today on the website virological.org, the groups agree that the outbreak was caused by the Makona tribe of a species called Zaire ebolavirus, just like the previous epidemic. A phylogenetic tree shows that the new virus falls between virus samples from the 2013–16 epidemic.
Until recently, scientists assumed that Ebola epidemics begin when a virus species jumps from an animal host to humans. Theoretically, this could happen in Guinea, says virologist Stephan Günther of the Bernhard Nocht Institute of Tropical Medicine, who worked with one of the three teams. But given the similarity between viruses from the epidemic and the new ones, “it must be incredibly unlikely.”
Outside, scientists agree, but say there has been no evidence for five years that Ebola was dormant in one person. “From the tree you would come to the conclusion that it is a virus that somehow persists in the area, and certainly, probably in a survivor,” said Dan Bausch, a veteran of several Ebola outbreaks. leading the public health of the United Kingdom. Quick support team. But it’s hard to rule out scenarios like a small, unrecognizable chain of human to human transmission, Bausch adds: ‘A survivor in 2014, for example, infected his wife a few years after recovery, infecting another man, surviving and carry virus for a few years and then infect another woman, who is then seen by a nurse who dies ”- the index case in the new outbreak.
It was not known that the nurse herself was a survivor, but she could have had contact with a survivor privately or through her work, or she could have been infected with few symptoms herself years ago. “Finding out what exactly happened is now one of the biggest questions,” Bausch says.
A further ongoing outbreak of Ebola in northern Kivu, in the Democratic Republic of Congo, was also initiated by transmission of someone infected during a previous outbreak, Delaporte said. (The survivor tested negative for Ebola twice after his illness in 2020.) It says people are now just as likely to be the source of a new Ebola outbreak as wildlife. “This is clearly a new paradigm for how these outbreaks begin.” Outbreaks caused by survivors may become even more likely, as increasing mobility and other factors have caused each Ebola outbreak to become larger, resulting in more survivors, says Fabian Leendertz, a veterinarian involved in the sequence. wash.
This is clearly a new paradigm for how these outbreaks begin.
The cases raise important new research questions, Bausch says, “How do we change our response to escape the outbreak-response-reintroduction-outbreak cycle?” he asks. “Can we use new medicine to remove viruses from survivors?”
But the most immediate question is what these results mean for Ebola survivors, who are already suffering greatly. Many have not only lost friends and family to the virus, but are also struggling with long-term effects, such as muscle aches and eye problems. In a study published in February, Delaporte found that about half of more than 800 Ebola survivors in Guinea reported symptoms two years after their illness, and a quarter after 4 years.
In addition, survivors experienced intense stigma. Many conspiracy theories have swirled in the wake of the epidemic, including the claim that survivors sold family members to international organizations to save themselves, says Frederic Le Marcis, a social anthropologist at the École Normale Supérieure in Lyon and the French Research Institute for Development, who works in Guinea. According to him, one man was the only one who survived out of 11 family members, and when he returned, no one wanted to work with him. “He was seen as untrustworthy.” News that a survivor has probably tackled the current outbreak could cause further problems for survivors, Le Marcis says: ‘Will they be highlighted as a source of danger? Will they be chased out of their own families and communities? ”
Alpha Keita, a virologist who led the sequence of CERFIG, is concerned about stigmatization and even violence against survivors has occupied him since he first achieved the surprising results a week ago. One important message to the public should be that some people infected with Ebola show few symptoms, which means that people can be survivors without knowing it. “So do not stigmatize Ebola survivors – you do not know that you yourself are not a survivor,” says Keita.
Bausch calls for an educational campaign that explains that unprotected sex with an Ebola survivor may pose a risk, but informal contacts such as handshakes and cooperation do not. And while there needs to be medical monitoring of survivors, it may not just be about testing them for Ebola virus, he says. “We need to acknowledge and help with all the other challenges, physical, mental and social, that survivors and their families face.” The key, according to Bausch, is to “not just treat survivors as a danger to hot potatoes to start a new outbreak.” It also poses a challenge to the country’s healthcare system if every patient with fever and diarrhea should be a potential case of Ebola, says Le Marcis.
Fortunately, Ebola vaccines and treatments have become available over the past few years. Thousands of contacts of the new Ebola patients, and contacts of these contacts, have already been vaccinated. Healthcare workers are also vaccinated. Vaccination of survivors can even help eliminate latent infections, Rasmussen says. And the fact that this time viral samples were followed up in Guinea shows that the scientific capabilities of the country have improved, Delaporte says: ‘Seven years ago, when the epidemic started, there was no infrastructure in Guinea to do so. . ‘