Epidemiology and Risk Profile of Ebola Cases Outside Africa, 1976–May 2026
This study has not yet been peer reviewed.
Background An outbreak of Bundibugyo ebolavirus in Ituri, Democratic Republic of the Congo was reported in May 2026. Neighbouring countries in Africa are at the greatest risk of cross-border spread, but the severe nature of Ebola virus disease has raised concerns globally around the risk of international transmission. Decision-makers outside Africa may be considering policies of varying stringency ranging from watchful waiting to border closures, and therefore need to understand the risks of Ebola importation in the context of previous epidemics.
Methods We conducted manual and AI-assisted searches to find all known Ebola cases that have occurred outside of the African continent and manually reviewed all identified case reports, public health bulletins and news articles to understand the risk of Ebola importation due to travel from Africa to other continents. We collected epidemiological data, including key dates, and analysed the historical risk of Ebola importation as well as the time-varying risk of Ebola importation during the 2014-2016 West African Ebola epidemic.
Results From the first recognised Ebola outbreak in 1976 to May 2026, there have been 28 confirmed cases of Ebola virus disease outside of Africa caused by epidemic-linked transmission of Zaire ebolavirus, Sudan ebolavirus, or Bundibugyo ebolavirus. Among these 28 cases, 21 (75%) were in individuals medically evacuated from Africa due to confirmed Ebola virus infection, three (11%) were in front-line health care workers returning from an Ebola outbreak whose symptoms were detected after border screening, one (4%) was in a traveller with no responsive role, and three (11%) were secondary cases in health care workers who treated another Ebola patient outside Africa. Based on Ebola epidemics since 2000, we estimated a crude overall risk of 0.81 Ebola cases outside Africa per 1,000 reported Ebola cases in Africa. Focusing on non-medically evacuated cases only, the crude overall risk is 0.17 Ebola cases outside Africa per 1,000 reported Ebola cases in Africa.
Interpretation The risk of undetected Ebola transmission outside Africa is low. Nearly all (27 of 28) confirmed Ebola cases reported outside Africa were linked to known occupational exposures, with reasons for travel specific to outbreak response. Our results suggest that the risk of case exportations could be substantially mitigated by infection prevention measures at the outbreak source and among outbreak response workers, in concert with enhanced travel screening and monitoring for returning response workers.