Rapid Risk Assessment: Outbreak of Ebola virus disease in West Africa - 13th update, 16 October 2015

Risk assessment
16 Oct 2015

European Centre for Disease Prevention and Control. Outbreak of Ebola virus disease in West Africa. 13th update, 13 October 2015. Stockholm: ECDC; 2015.

​On 9 October 2015, the United Kingdom notified the appearance of an unusual late complication, more than eight months after initial recovery, in an Ebola survivor who was infected while working as a healthcare worker in West Africa. As a precautionary measure, 40 close contacts of the case were offered vaccination.
The situation in West Africa is improving further: Liberia was declared Ebola-free on 3 September 2015. Guinea and Sierra Leone report only low-level transmission.

Executive summary

Updated rapid risk assessment  
ECDC’s new rapid risk assessment on the West Africa Ebola virus disease outbreak re-assesses the risk of importation of Ebola virus to the EU and the risk of onward transmission following the decline of the outbreak observed in Guinea and Sierra Leone. It also considers the risks associated with a patient in the UK showing an unusual late complication of Ebola infection.  On 9 October 2015, the UK notified an unusual late complication in an Ebola survivor. The case is a nurse who was diagnosed with EVD on 29 December 2014, after returning from Sierra Leone to Glasgow. She was declared free of Ebola on 24 January 2015. The risk of further transmission from this nurse is considered very low, given the preventive measures taken and the continued monitoring of close contacts.  Further investigations are needed to fully understand the mechanism and impact of the re-appearance of viral RNA in this patient more than eight months after recovery. Ongoing cohort studies will hopefully provide more information about EVD survivors’ complications and long-term prognosis The risk of EVD being imported into the EU has decreased to an extremely low level. The risk of further transmission in the EU from an imported case remains very low.  The re-emergence of EVD transmission in West-Africa remains possible as a result of transmission from a recovered case through contact with infected bodily fluids (e.g. through sexual contact), unrecognised or asymptomatic cases, or from reintroduction from the animal reservoir. 

Recent studies on sexual transmission of the Ebola virus 
Two studies published on 14 October in the New England Journal of Medicine provide insights into sexual transmission of Ebola virus and the duration of virus persistence in semen. The first study by Mate et al supports evidence of sexual transmission from a convalescent male survivor to his partner 179 days after the onset of disease, and 155 days after the clearance of Ebola virus from his blood. The second study by Deen et al summarises the results of a longitudinal monitoring of Ebola virus genetic material (RNA) in semen among survivors, demonstrating the presence of viral RNA in semen up to nine month after disease recovery.Both studies are providing important findings on the sexual transmission of EVD and the potential persistence of the virus into semen. They need to be taken into account during the follow-up of the EVD survivors.