Scientists trace Ebola's genetic path in Africa, weighing role of mutations

Scientists are using blood samples collected throughout the Ebola outbreak to map the virus’ spread from country to country by tracking tiny mutations in its gene sequences. The picture is not yet complete, but intriguing discoveries have been made. Virus mutations first detected in Sierra Leone last spring were found later in Liberia and Mali, and scientists are examining whether this resulted from the chance movements of people across borders.