The first recorded Ebola outbreak was in 1976 in Zaire (now, the Democratic Republic of Congo) and Sudan. Since then, the dark reality of the virus began to surge gradually throughout the world and the most severe Ebola outbreak began in Guéckédou, Guinea, West Africa in December 2013.
Despite the Ebola outbreaks in different countries ended after some times the inception of Ebola virus, experts are yet to get to the bottom of the actual mode of transmission of Ebola virus.
However, a study at Harvard University has unfolded a number of Ebola’s secrets and critical facts including that the virus was being transmitted only by person-to-person contact, after they have sequenced more than 200 additional genomes from Ebola virus samples. This study on sequencing the genome of this deadly virus reveals new insights into long-term Ebola outbreak.
The study also revealed that the virus was picking up new mutations through its many modes of transmission.
The study was done in collaboration with many notable institutions including the Broad Institute, the U.S. Centers for Disease Control and Prevention (CDC), and the National Institute of Allergy and Infectious Diseases (NIAID, part of the National Institutes of Health) and some other.
Hopefully, with this collaborative effort, scientists should be able to capture the fullest picture yet of how the virus is transmitted and how it has changed over the long-term outbreak. The team also made their data available in public in an effort to enhance global response.
Pardis Sabeti, senior author of the study said, “One of the most rewarding aspects of working in this outbreak response is the connections we have made with so many extraordinary individuals through open data sharing.”
“Our early work tracked the virus’s movements over just three weeks as the Ebola outbreak emerged in Sierra Leone. Now with a view of the virus over seven months, we can understand how it has been moving and changing over the long-term.”
“One insight we gained from this high-resolution sequence data is that later in the outbreak, there was very little cross-border exchange of the virus. That’s important, because the three main affected countries–Sierra Leone, Liberia, and Guinea–are often described as having ‘porous borders’ which allowed people to travel back and forth,” said Danny Park, lead author of the study
“While cross-border contact may have helped fuel the early days of the outbreak, it’s now clear that, once underway, the virus didn’t migrate in the ways many had predicted. This is very reassuring to know that measures to contain the outbreak at borders can work and allows attention to be focused on within-country movement.”
The study also provides insight into viral evolution over the sustained outbreak. The spreading of Ebola virus results in accumulation of many mutations and if there is unequal share of mutations it could affect protein function. The researchers noted that these mutations were likely to be damaging to the virus, but the outbreak hadn’t gone on long enough for natural selection to weed them out yet.
“Ebola has never been exposed to humans for so long, and through so many transmissions, it has begun to weed out mutations that do not benefit it,” said Park.
The team also found that these mutation did not last very long, and the rate of change in the viral genome may not be what is expected. However, the team identified other changes of the virus that are expected over the longer-term.
For example, in some patients, they saw evidence of viral genomes being edited by human enzymes, which is something that has been never seen for Ebola and is only seen previously with viruses that have long-interacted with humans.
Sabeti said, “the many mutations we saw early in the Ebola outbreak and the evolution we saw over the long-term have been observed for other viruses before, and the genomic data only helps illuminate known evolutionary phenomena.”
“The data just remind us what we have always known, that we must get this viral lineage to zero.”