Analysis of the genome of the virus which has been circulating in Africa, particularly in Guinea, since February shows that it is the same strain as that which raged between 2013 and 2016.
- The analysis of the strain of the virus indicates a transmission between humans, which can justify the thesis according to which the virus was hidden for 5 years in the body of a survivor.
- In 2016, a study showed that the virus is able to survive 500 days in the body before being transmitted again.
- Another researcher considers it possible that a chain of human-to-human transmission has passed under the radar for all these years.
Since the end of January, the Ebola virus has returned to Guinea. At least 192 cases have been identified by theWorld Health Organization (WHO) as of February 15, date of the last census. By looking for the strain of the virus responsible for this epidemic resurgence, scientists have realized that it is almost identical to the one that hit the region between 2013 and 2016 and killed more than 11,000 people. Three independent analyzes of the virus genome hypothesize that the virus actually slept for five years in the body of a survivor of the previous outbreak. These findings were reported on March 12 in the journal Science.
A return five years later, unheard of
A 51-year-old nurse has been identified as “patient zero” in this outbreak. She was first diagnosed with typhoid fever and then with malaria before dying on January 28 of the Ebola virus. 1er February, his burial, where no health measures were respected, seems to be the trigger for the transmission of the virus. Members of her family, as well as a doctor she had consulted, contracted symptoms of the disease such as diarrhoea, vomiting and bleeding. Four have since died and two others have been placed in quarantine.
By analyzing the strain of the virus responsible, named EBOV, the scientists concluded that it belongs to the line Makona of the Zaire species, just like the strain of the 2013-2016 epidemic. This means that the return of the virus is the result of human-to-human contamination. “To see a new outbreak appear from a latent infection five years after the end of an epidemic is unheard of and it is frighteningwrote in Science Éric Delaporte, specialist in infectious diseases at the University of Montpellier and who is part of one of the three teams to have analyzed the genome of the virus currently circulating in Guinea. Epidemics triggered by Ebola survivors remain very rare but they pose a delicate problem: how to prevent them without stigmatizing those who have survived the disease?
Other possible explanations
To explain this return of the virus with an almost identical strain, the researchers put forward the hypothesis that it would have remained latent in the body of a survivor for at least 5 years before it infects the nurse who died at the end of January. A previous study, published in 2016 in the journal Clinical Infectious Diseases, has indeed shown that the virus is able to survive 500 days in the body before being transmitted again. The researchers then estimated that the virus would have hidden in the testicles which have an immune privilege, that is to say that a pathogenic agent can be there without this triggering an inflammatory reaction. The same phenomenon would be at work but, this time, over a much longer time.
Research continues and new explanations could be put forward. For Dan Bausch, a researcher who works on several outbreaks of Ebola virus disease and who participated in the study published in Science, genomic analysis is not enough to conclude that the virus lay dormant for 5 years in a survivor. According to him, it is possible that a human-to-human chain of transmission has passed under the radar for all these years. “Understanding what exactly happened is currently one of the biggest questions”he concluded.
.
