Although researchers had initially feared that the current Ebola outbreak had begun as the virus repeatedly jumped from a natural reservoir (represented most likely by infected animals) to humans, recent research has shown that in fact, it stemmed from an initial leap into humans. Scientists have concluded that the deadly virus spreading in several West African countries has descended from an original viral jump and that there are no new versions of the pathogen being introduced into the human population.
The research provides
“powerful evidence that once the virus was introduced into the human population subsequent transmission was human to human, and this is not from repeated introductions from the wild,”
William Schaffner, expert in infectious diseases at the Vanderbilt University, said.
This finding practically validates the public health response that governments have had when facing this outbreak, because it focused on tracking and treating infected citizens instead of keeping them away from potential animal sources.
Researchers analyzed over 95 Ebola virus genome sequences found in approximately 70 percent of all Ebola patients that have been diagnosed in Sierra Leone between May and mid-June. After extracting the virus samples from the blood of patients, scientists concluded that the first case of the disease in Sierra Leone was that of a traditional healer who had been working with Ebola patients in Guinea and had been buried in the country. The thirteen women who attended the healer’s burial developed the disease.
However, in spite of this discovery, researchers still cannot pinpoint the source of the initial infection: whether it was infected meat, an infected fruit bat or something completely different. While a study published in the New England Journal of Medicine suggested that the current strain of Ebola is related to the Zaire strain of the virus, researchers can’t explain how this particular pathogen made the leap into the human population. What this discovery shows, however, is that the current outbreak agent is related to the 1976 Ebola strain and is not a co-evolved strain of the virus (as some epidemiologists believed early in the outbreak).
Despite it being related to the 1976 virus, the current strain has suffered over 300 mutations compared to the 1970s strain, researchers say. What is most worrisome, however, is the fact that the virus seems to be rapidly mutating: scientists have compared reference sequences collected from patients in Guinea just a few months earlier and noted that 55 small mutations have already taken place in the virus’ structure.