New genetic research seems to confirm a fear researchers had about a fatal Ebola outbreak in Guinea in February: The source of the outbreak was probably the dormant remains of the virus in a survivor who caught it at least five years earlier. The discovery could complicate efforts to curb the viral disease that emerges.
In late January 2021, a 51-year-old female nurse in the West African country fell ill with Ebola (formally known as Ebola virus disease or EVD). Like many victims, she initially experienced vague symptoms such as headaches, nausea, and general weakness. Although she was hospitalized, her doctors had unfortunately misdiagnosed her with malaria and a salmonella infection, and she was sent home after two days. She fell ill again at home and died three days later.
After her death, her husband and other family members attending her funeral also became ill, and four would eventually die. These cases finally warned national health officials. In mid-February, blood tests confirmed the outbreak and health workers rushed to check it. Between February and June 2021, when the outbreak was formally declared over, 16 confirmed cases were reported along with 12 deaths.
Typically, Ebola outbreaks start with zoonotic transmission from an infected animal to a person where certain bats are thought to be the primary host of the virus. However, early analysis of the first blood samples collected from victims during this outbreak indicated that something else was going on. The virus seen in their blood was very similar to a variant collected from survivors of the West African outbreak of Ebola 2013-2016, the largest and deadliest epidemic of the virus to date, with over 11,000 deaths. Scientists soon suspected the virus had resurfaced somehow from a human host years later and killed again.
This new study, published Wednesday in the wild, all except seals who think they are right. Researchers in Guinea, France and Germany carried out next-generation genetic sequencing of the virus collected from 12 victims of the outbreak and used it to construct complete or near-complete genomes of the virus. They then used this information to build a pedigree of the trunks and compared them to the virus that floated around five years ago.
The virus, found in Guinea this year, was actually closely linked to the virus seen during the previous West African outbreak, the authors said, indicating “that the new outbreak was not the result of a new flood from an animal reservoir.” Moreover, they did not find signs of much genetic divergence between then and now, suggesting that it was not strongly transmitted between humans all the time. Instead, the source virus may have caused a persistent but slowly infected infection with reduced reproduction in a survivor, or it could have gone completely latent and then reactivated for an unknown reason, making the survivor contagious again.
Researchers have that known since the West African outbreak that the virus can survive unnoticed in victims for some time after they have fully recovered, especially in pockets of the body where the immune system is less active, such as. the eyes or semen. But the longest known time between a person who became infected with the virus and transmitted it to another or became ill again before this was about a year and a half. A much larger window for virus transmission means that communities may be more vulnerable to future outbreaks than currently thought. It can also make the lives of survivors who already tend to experience discrimination and prejudice from others even more difficult, the authors warn.
“The human origins of the EVD outbreak in 2021 and the associated shift in our perception of the EBOV outbreak require careful attention to survivors of the disease,” they wrote. “The concern that survivors will be stigmatized as a source of danger should be a matter of careful attention.”
In this case, it is possible that the unknown patient zero may have transmitted the virus during intercourse. However, given that the first new victim was a nurse, the patient may also have experienced a resurgence of symptoms that led to a health visit and transmission at that time. The nurse herself may have had a dormant infection left, although it is less likely as she had no previously documented case.
In the big picture, the authors say these findings should fuel research to find a way to keep survivors virus-free and protect communities after an outbreak has subsided.
“In addition to the importance of appropriate health measures focused on survivors, the late resuscitation of the virus also highlights the urgent need for further research into potent antiviral agents that can eradicate the latent virus reservoir in patients with EVD and for effective vaccines that provides long-term protection, ”they wrote.