Epidemiological update: Outbreak of Ebola virus disease in West Africa

Epidemiological update

​An update on the current epidemiological situation of the ongoing outbreak of Ebola virus disease in West Africa.

​Since December 2013 and as of 16 November 2014, WHO has reported 15 145 confirmed, probable and suspected cases of Ebola virus disease (EVD) in six affected countries (Guinea, Liberia, Mali, Sierra Leone, Spain and the United States of America) and two previously affected countries (Nigeria and Senegal).

There have been 5 420 reported deaths. This is an increase of 1 047 cases and 260 deaths since 11 November 2014.

Distribution of cases

Countries with widespread and intense transmission: • Guinea: 1 971 cases and 1 192 deaths (as of 16 November 2014),
• Liberia: 7 069 cases and 2 964 deaths (as of 15 November 2014),
• Sierra Leone: 6 073 cases and 1 250 deaths (as of 16 November 2014).
 Countries with an initial case or cases, or with localised transmission:
• United States: four cases including one death,
• Spain: one case, no deaths,
• Mali: six cases, five deaths,
• Nigeria: 20 cases and eight deaths. Nigeria was declared Ebola free on 19 October 2014,
• Senegal: one confirmed imported case. Senegal was declared Ebola free on 17 October 2014.
 

Distribution of cases of EVD by week of reporting in Guinea, Sierra Leone, Liberia, Nigeria, Senegal and Mali, weeks 48/2013 to 47/2014, as of 16 November 2014.

* In week 45/2014, WHO carried-out retrospective correction in the data resulting in reporting 299 fewer cases resulting in a negative value for new cases in week 45 which is not plotted.** According to WHO the marked increase in the cumulative total number of cases in week 43 is due to a more comprehensive assessment of patient databases leading to 3 792 additional reported cases. However, these cases have occurred throughout the epidemic period. The green line represents the trend based on a five week moving average plotted on the fifth week of the moving average window. The figure includes cases in Nigeria (20), Senegal (1) and Mali (4).
 

Situation in specific West African countries

According to WHO, in the three countries with widespread and intense transmission, reported case incidence seems stable in Guinea and Liberia, but is still increasing in Sierra Leone. All administrative districts in Liberia and Sierra Leone have reported at least one confirmed or probable case of EVD since the start of the epidemic. Cases and deaths continue to be under-reported.
 
In Mali, there have been six cases, five confirmed and one probable, including five deaths. The last five reported cases have occurred in the Malian capital Bamako, and are not related to the country’s first EVD-positive patient, who died on 24 October. All identified contacts connected with this initial case have now completed 21-day follow-up. Among the cases in Bamako, two are HCWs who cared for an imported case from guinea who was admitted in a Bamako clinic on 25 October. According to Mali Ministry of Health 352 out of 413 (85%) identified contacts are followed.
 

Distribution of cases of EVD by week of reporting, Guinea, Liberia and Sierra Leone, as of week 47/2014.

* The marked increase in the number of cases reported in Sierra Leone (week 44) and Liberia (week 43) results from a more comprehensive assessment of patient databases. The additional 3 792 cases have occurred throughout the epidemic period. Source: Data are based on official information reported by ministries of health up to the end of 2 November for Guinea and Sierra Leone and 31 October for Liberia.).** In week 45/2014, WHO reported 476 fewer cases than the week before in Sierra Leone due to retrospective corrections.§ In week 44/2014, WHO reported zero cases for Liberia.

Distribution of cases of EVD by week of reporting in Guinea, Sierra Leone and Liberia (as of week 46/2014).

Source: Data from ministries of health reports (suspected, probable and confirmed cases).

 

Situation among healthcare workers

As of 16 November WHO reported a total of 585 health-care workers (HCWs) infected with EVD, 335 of whom have died. According to WHO early indication a substantial proportion of infections among HCWs occurred outside the context of Ebola treatment and care centres.

 

Number of Ebola cases and deaths among healthcare workers, as of 16 November 2014.

Country Healthcare worker cases (% of reported cases) Healthcare worker deaths (% of reported deaths)
Guinea 95 (4.8) 55 (4.6)
Liberia 341 (4.8) 170 (5.7)
Mali 2 (33.3) 1 (25.0)
Nigeria 11 (55.0) 5 (62.5)
Sierra Leone 132 (2.2) 104 (8.3)
Spain 1 (100) 0
United States 3 (75.0) 0
Total 585 (3.9) 335 (6.2)

Source: Data are based on official information reported by Ministries of Health.

Situation outside West Africa

USA
No new autochthonous EVD cases have been reported since 23 October. The latest autochthonous reported case concerns a medical aid worker who volunteered in Guinea and recently returned to the United States. He was hospitalised in New York City and was discharged healthy on 11 November 2014.Spain
No new cases have been reported since 6 October when a healthcare worker was infected while caring for an Ebola-infected patient in Madrid. She recovered and tested negative for EVD on 19 October. A second negative test was obtained on 21 October. All 83 contacts of the HCW have completed a 21-day follow-up. Spain will be declared free of EVD 42 days after the date of the second negative test if no new cases are reported.