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An international research team has rapidly sequenced 99 Ebola virus genomes collected in the 2014 outbreak. The team, which includes members from the Broad Institute, Harvard University and the Sierra Leone Ministry of Health and Sanitation, holds out hope that the findings will help multidisciplinary, international efforts to understand and contain the epidemic that is currently exploding in West Africa. Before their research was published, five of the team members died of Ebola. The 99 genomes that they studied came from a total of 78 patients diagnosed with Ebola in Sierra Leone during the first 24 days of the outbreak. Since some patients gave more than one sample, the team was able to see how the virus changed over the course of a single infection.
Through deep sequencing techniques, the team increased the amount of data available on the Ebola by four-fold. The results revealed that the 2014 Ebola virus genomes contain over 300 mutations that distinguish them from previous outbreaks. They also found clues that suggest that the 2014 outbreak started from a single introduction into humans before spreading among them over many months. Fruit bats are thought to be the natural host of Ebola, which first appeared among humans in the 1970s. The 2014 outbreak is unprecedented in both its size and the fact that it emerged in highly populated parts of West Africa, as opposed to sparsely populated areas in Central Africa as before. Previously, the largest outbreak was in 1976 and reported 318 cases. The current outbreak, however, has reported over 2,000 cases and over 1,000 deaths. According to the World Health Organization (WHO), the current outbreak has infected more than 240 health care workers in West Africa, more than half of whom have died.
According to the study, the 2014 Ebola strains most likely have a common ancestor back in the 1976 outbreak, and suggests that the strains in the current West African outbreak separated from the Central African version in the past 10 years. The mutations in the 2014 Ebola strains are mostly in genes that code for proteins, which is important for researchers looking to keep track of how the virus is changing. With this is in mind, the researchers released the genome sequences to the international scientific community before finally publishing their study. By making the data immediately available to the community, the researchers hope to accelerate response efforts. The study presents a catalog of 395 mutations, over 340 of which distinguish the current outbreak from previous ones, and over 50 of which have exclusively occurred during the current outbreak.