Ebola virus in survivors can trigger outbreaks years after infection

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TOKYO: Ebola survivors can relapse and trigger outbreaks at least five years after infection, and long-term follow-up of former patients is needed to prevent devastating outbreaks, according to new research.
Scientists already knew that Ebola could remain inactive in survivors, whose results were negative because the virus is in the tissues rather than circulating in the blood.
But analysis of an outbreak this year in Guinea, published Wednesday in the journal Nature, found that these “virus reservoirs” appear capable of awakening and causing new infections and transmission years later.
To trace the source of the Guinea outbreak, which involved 16 confirmed cases, 12 of which died, the researchers analyzed the genomes of samples from various patients.
Ebola outbreaks are generally believed to be the result of the virus being “spilled” from a host animal to a human.
But the analysis showed that the Guinea strain was practically identical to that of a 2013-16 wave.
If the virus had been actively circulating in the community since then, it would have accumulated a certain number of mutations as it spread.
In contrast, the 2021 virus had only 12 changes, “much less than would be expected … during six years of sustained person-to-person transmission.”
That strongly suggests that the source was a reactivated virus that had lain dormant in a survivor, he said. Alpha Keita, researcher of the Montpellier University who led the study.
“This is the longest known time between the declared end of an epidemic and a viral resurgence,” he told AFP.
“It is a new paradigm: the possibility that transmission from an infected individual during a previous epidemic could be the source of a new outbreak.”
How and why a dormant Ebola virus suddenly wakes up and sickens a person remains a mystery, although there are some tantalizing clues.
Sometimes a rise in Ebola antibodies can be detected in survivors at any given time, a possible sign that the body is responding to a resurgent virus.
About two-thirds of Ebola survivors have high antibody levels even five years after infection, but “the question to ask is what happens if there is a resurgence in people whose immunity has decreased,” Keita said.
The study findings have “considerable implications for the public health and care of Ebola survivors,” said Robert F. Garry of Tulane University School of Medicine.
“Humans can now be added to the list of intermediate hosts that can serve as long-term ‘reservoirs’ for the Ebola virus and trigger new outbreaks,” he wrote in a review commissioned by Nature.
Health workers need to be prioritized for vaccination and monitor Ebola survivors for signs of an outbreak, he added.
Keita said a broader definition of “Ebola survivor” is now needed, beyond those who battled symptoms.
Even asymptomatic people “could be the starting point” of an outbreak, he warned.
“We need a real, long-term follow-up protocol … so that we can detect the resurgence of previously infected people early.”
However, he warned that monitoring must be done with caution to avoid ostracism of survivors, a point echoed Trudie lang, Director of the Global Health Network at the University of Oxford.
“These people are considered heroes by some for surviving,” he said.
“However, (they) could also be stigmatized and excluded if there is a fear that these people pose a risk.”
Lang, who was not involved in the study, said it offered “impressive new findings.”
The study illustrates “what we still don’t understand, but what we really need to learn, if we are to deal with these dangerous threats,” he added.
Moving forward, Keita wants to see work on the causes of the viral resurgence and research on eradicating Ebola reservoirs in survivors.
“We have to look at Ebola as a global problem,” he said.
“Every individual exposed to the virus who had a strong serological (antibody) response could be the starting point for a new resurgence.”





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