Epidemiological update: outbreak of Ebola virus disease in West Africa

Since December 2013 and as of 21 September 2014, WHO reports 6 262 cases of Ebola virus disease (EVD), including 2 917 deaths, in Guinea, Liberia, Nigeria and Sierra Leone. This is the first outbreak of EVD in West Africa and it is unprecedented in size and geographical distribution, affecting densely populated urban areas.

Three hundred seventy three of the cases occurred in healthcare workers, including 208 deaths. The outbreak continues to increase rapidly and the reported figures are believed to be underestimations of the real magnitude. WHO reported 915 new cases and 287 deaths since the previous ECDC update of 19 September.

A recent study published by the WHO Ebola Response Team forecasts more than 20 000 (5 740 in Guinea, 9 890 in Liberia and 5 000 in Sierra Leone) by beginning of November 2014.

To date, no cases have been found to be positive outside Guinea, Liberia, Nigeria or Sierra Leone, except for one imported case in Senegal (a Guinean citizen who arrived from Guinea).

Distribution of reported cases of EVD by week in Guinea, Sierra Leone, Liberia, Nigeria and Senegal, week 48/2013 to 39/2014 (data as of 21 September 2014*)

Source: adapted from WHO*The bar for week 39/2014 does not represent a complete week.

Distribution of confirmed, probable and suspected EVD cases by district and week of reporting, weeks 33-38, 2014

 *Source: adapted from national situation reports, when available.

Cases and deaths of EVD, West Africa affected countries, as of 21 September 2014, week 39

Source: adapted from WHO

Distribution of cases of Ebola virus disease by week of reporting in Guinea, Liberia, and Sierra Leone, as of 21 September 2014

Source: Adapted from WHO, data for week 39 are incomplete.