The 2 year old boy who died in December 2013 in Gueckedou, Guinea, is considered the index case of the current outbreak of Ebola virus disease caused by the Zaire species. Up until 2014, the disease was limited to rural areas of east and central Africa, but it has now spread to Liberia, Sierra Leone, Nigeria, and Senegal.

Ebola is a deadly virus that causes frequent disease outbreaks in the human population. Here, we analyse its rate of new introductions, case fatality ratio, and potential to spread from person to person. The analysis is performed for all completed outbreaks, and for a scenario where these are augmented by a more severe outbreak of several thousand cases. The results show a fast rate of new outbreaks, a high case fatality ratio, and an effective reproductive ratio of just
less than 1.

n October 1976, the government of Zaire (now the Democratic Republic of Congo [DRC]) asked what was then the U.S. Center for Disease Control, where we worked, to join an international group of scientists in elucidating and controlling an outbreak of an unusually lethal hemorrhagic fever.