Genetic analysis now leaves no doubt: the new outbreak of Ebola in the first half of 2021 in Guinea was the result of a reactivation of the virus in an ex-patient. From 2013 to 2016, Guinea, along with Sierra Leone and Liberia in West Africa, was the scene of the largest Ebola outbreak in recorded history, with more than 28,000 infections and 11,000 deaths. The fact that the exact same virus appears five years later proves that humans themselves can be a reservoir for the Ebola virus. That’s what international researchers are writing this week Nature.
Because of its great importance, the researchers already shared the main point of their finding with their colleagues in March via the site virological.org. They analyze all the details in the publication in Nature.
The new outbreak in Guinea started when a 51-year-old woman from Gouéké was hospitalized on January 21 with headaches and abdominal pain, nausea, weakness and dizziness. She was sent home diagnosed with malaria and food poisoning. As she continued to feel ill, she visited another hospital and a traditional healer. She died three days later.
After her funeral, several family members became ill, including her husband. Laboratory tests showed that it was an Ebola infection. Guinea’s health authorities declared on February 14 that there was another Ebola outbreak. Contacts of the victims were quickly traced and vaccinated. More than ten thousand direct and indirect contacts and healthcare workers received a shot. After two more reported infections in April, it remained calm; the authorities declared the epidemic over on June 19. The outbreak was limited to 16 confirmed infected people, 12 of whom died.
The genetic makeup of the Ebola virus could be deciphered from twelve patients, and it turned out that the virus was very similar to the virus that was floating around during the great epidemic in 2016. It contained the same ten characteristic mutations. The researchers calculated that the most recent ancestor of the 12 viruses analyzed must have originated around January 22, 2021 – around the date the 51-year-old woman became ill.
It is therefore certain that the Ebola virus has “hidden” in a person’s body, says virologist Martine Peeters of the University of Montpellier and one of the authors of the study. “If the virus originated from an undetected chain of infection in the population, we would see many more mutations. Had it re-entered humans from wild animals, it would appear as a separate offshoot of the Ebola virus genetic tree. But the 2021 virus falls right in the middle of the cluster of viruses we saw in Guinea in 2016.”
It is not known how the woman from Gouéké contracted the virus. During the great epidemic of 2013-2016, she had not been ill, nor had she been in contact with Ebola patients. As far as can be ascertained, she has not come into contact with Ebola patients through her work as an obstetrician. According to Peeters, it remains a guess. “She may have been infected through sex with someone who survived Ebola, or she may have had mild Ebola at the time, so she was not tested and registered.”
Even though that last piece of evidence is missing, the conclusion is convincing, says Professor of Tropical Medicine Martin Grobusch of Amsterdam UMC. “The news that an epidemic can suddenly start again in someone who was ill years ago and who can then infect others without noticing, took our breath away,” says Grobusch. “The virus can sometimes still be detected in the body fluids of people who have survived Ebola, especially in semen. This was known to pose a risk of a resurgence a few months to at most two years after an outbreak. The fact that this is apparently still possible five years later does give a feeling of powerlessness.”
It raises the question of whether new measures are needed to fight Ebola. The authors suggest vaccinating all people around ex-patients and perhaps the ex-patients themselves. Grobusch is hard-headed: “Mass vaccination is not the solution, given the still limited supply of vaccines and the fact that it is not known how long they provide protection. I see more in targeted vaccination of risk groups during an outbreak, direct contacts of patients and medical staff who treat patients. That is how it has now happened.”
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Also the suggestion in the Naturearticle to eradicate the latent virus from ex-patients with drugs, Grobusch does not see as an option. “We are not there yet. The best drug we have now, remdesivir, is at best moderately effective against Ebola. The question is whether it will be possible at all to clear up dormant residual virus with medicines. That is difficult because, for example, we have not yet succeeded in doing so with other infectious diseases such as HIV or tuberculosis.”
The fact that recovered Ebola patients can still be a source of new infections after years is extremely sensitive. Stigmatization and exclusion are lurking. “The only thing we can do about that is put it into perspective,” Grobusch says. “What we have now seen is an oddity. And it’s not surprising that we see it in West Africa, because here was the largest outbreak ever. However, the risk is very small. Of the 17,000 survivors in West Africa, perhaps a handful of men still have detectable virus in their semen.”
That is why it is better to invest the energy in detecting new outbreaks. And that’s the good news, Grobusch says, because apparently things are going really well. “The alertness is very high, and that means that you can stop an outbreak whether it comes from people or animals very quickly.” As an example, he cites the discovery of a Marburg infection in a man who became ill in early August, not far from where the Ebola outbreak had taken place. “Of course people were immediately afraid that it was Ebola again. But it turned out to be Marburg, a closely related hemorrhagic virus. Thanks to quick intervention and isolation of contacts, it was limited to this one contamination. This is a victory: it shows how strong and effective the vigilance is in this region.”