New insights into the genetic evolution of the ongoing Ebola virus outbreak in West Africa are reported in Nature this week. The analysis shows how different lineages of the virus evolved and spread in West Africa, between Sierra Leone, Guinea and Liberia.
The current Ebola virus outbreak has been traced back to transmission from a bat to an infant in Guinea in December 2013, from which it spread throughout Guinea, Sierra Leone and Liberia. The origin of the particular virus in each country and the time of transmission have been unclear, but the new information presented by Miles Carroll and colleagues helps to address these questions. They analyse 179 new virus sequences from patient samples collected in Guinea between March 2014 and January 2015. The study pinpoints the origins of the virus in each affected country and narrows down the timing at which each particular virus was transmitted; for example, they find that the Ebola virus from Guinea probably spilled over into Sierra Leone in April or early May 2014.
To date there have been over 27,000 reported cases and over 11,000 deaths attributed to the ongoing Ebola virus outbreak. Data from this new analysis could be used to assess how effective control measures have been and helps us to understand how the current outbreak has been evolving.