The Ebola viruses behind a new outbreak in Guinea are surprisingly similar to the viruses identified during the major outbreak in West Africa that lasted from 2013 to 2016, according to a new genetic analysis. The finding suggests that the virus may have persisted silently in a survivor for at least five years and that the current outbreak was triggered by that unfortunate person, rather than an overflow from an animal reservoir.
In the genetic analysis posted online on Friday, a group of international researchers reported that Ebola viruses collected from the current outbreak in Guinea have only a dozen or more genetic differences from Ebola variants collected in the same area of Guinea in 2014. Based on in what researchers know about the rate at which Ebola collects these genetic substitutions – its rate of evolution – that number of accumulated differences should have totaled more than 110 in that time span, not 12.
“This number of substitutions is much lower than expected during sustained human-to-human transmission,” wrote the researchers in their analysis. Instead, they note that this rate of slow evolution is a “hallmark of persistent infections”.
“Therefore, the Guinea cluster index case of 2021 was probably infected from a persistent source, such as via sexual transmission from a [Ebola] survivor ”, they conclude.
The Ebola virus is known to persist in some survivors, especially in places where it can be detected by the immune system, such as the testicles or eyes. A 2016 study reported the resurgence of the virus in a survivor’s seminal fluid more than 500 days after the initial infection.
Still, the period of more than five years was “shocking”For many virologists and public health experts. And that raises a number of concerns for the many survivors of past outbreaks, some of whom may have had mild cases of Ebola without realizing it. In particular, many people who have survived Ebola face stigmatization, and the possibility of years of persistence is likely to amplify this problem.
In the 2013-2016 outbreak in West Africa, more than 28,000 people were infected with the virus and more than 11,000 died. It is the biggest Ebola outbreak in history. Most cases and deaths occurred in Guinea, Liberia and Sierra Leone. The outbreak began with a case reported in an 18-month-old boy in December 2013; the boy is believed to have contracted the virus from bats.
The current outbreak, which was declared on February 14, fell ill at least 18 and killed nine. Vaccination efforts are now underway to prevent the virus from spreading.