Real-Time Assessment of the International Spreading Risk Associated with the 2014 West African Ebola Outbreak

  • Ana Pastore-Piontti
  • Qian Zhang
  • Marcelo F. C. Gomes
  • Luca Rossi
  • Chiara Poletto
  • Vittoria Colizza
  • Dennis L. Chao
  • Ira M. Longini
  • M. Elizabeth Halloran
  • Alessandro VespignaniEmail author


The 2014 West African Ebola Outbreak is the largest Ebola virus disease (EVD) epidemic ever recorded, not only in number of cases but also in geographical extent. Unlike previous EVD outbreaks, the large number of cases observed in major cities with international airports raised the concern about the possibility of exportation of the infection in countries around the world. Starting in July 2014, we used the Global Epidemic and Mobility model to provide a real-time assessment of the potential international spread of the EVD epidemic. We modeled the unfolding of the outbreak in the most affected countries, considered different scenarios reflecting changes in the disease dynamic, and provided estimates for the probability of observing imported cases around the world for 220 countries. The model went through successive calibrations as more surveillance data were available, providing projections extending from a few weeks to several months. The results show that along the entire course of the epidemic the probability of observing cases outside of Africa was small, but not negligible, from September to November 2014. The inflection point of the epidemic occurred in late September and early October 2014 with a consistent longitudinal decrease in new cases, thus averting the status quo epidemic growth that could have seen hundreds of exported cases at the global scale in the following months.


Ebola Epidemic West Africa Large scale model International spread Agent-based model Computational model 



We acknowledge funding from DTRA-1-0910039 and MIDAS-National Institute of General Medical Sciences U54-GM111274. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. MFCG acknowledges CNPq-Brazil fellowship 314164/2014-6. We thank Nicole Samay for her invaluable help in the editing and preparation of the figures of the manuscript.


  1. 1.
    Feldmann, H., Geisbert, T.W.: Lancet 377, 849–62 (2011)CrossRefGoogle Scholar
  2. 2.
    World Health Organization. Ebola key facts.
  3. 3.
    ECDC: Outbreak of Ebola virus disease in West Africa. Third update (2014). Accessed 1 Aug 2014Google Scholar
  4. 4.
    Ebola ça Suffit Ring Vaccination Trial Consortium. BMJ 351, h3740 (2015)Google Scholar
  5. 5.
    Henao-Restrepo, A.M., Longini, I.M., Egger, M., Dean, N.E., Edmunds, W.J., Camacho, A., Carroll, M.W., Doumbia, M., Draguez, B., Duraffour, S., et al.: Lancet 386(9996), 857–866 (2015)CrossRefGoogle Scholar
  6. 6.
    World Health Organization: Ebola Situation Report. Accessed 15 Dec 2015
  7. 7.
    World Health Organization: Statement on the 1st meeting of the IHR Emergency Committee on the 2014 Ebola outbreak in West Africa. Accessed 15 Dec 2015
  8. 8.
    Balcan, D., Hu, H., Goncalves, B., Bajardi, P., Poletto, C., et al.: BMC Med. 7, 45 (2009)CrossRefGoogle Scholar
  9. 9.
    Balcan, D., Colizza, V., Goncalves, B., Hu, H., Ramasco, J.J., et al.: Proc. Natl. Acad. Sci. 106, 21484–21489 (2009)CrossRefGoogle Scholar
  10. 10.
    Balcan, D., Goncalves, B., Hu, H., Ramasco, J.J., Colizza, V., et al.: J. Comput. Sci. 1, 132–145 (2010)CrossRefGoogle Scholar
  11. 11.
    Legrand, J., Grais, R., Boelle, P., Valleron, A., Flahault, A.: Epidemiol Infect 135, 610 (2007)CrossRefGoogle Scholar
  12. 12.
    Brockmann, D., Schaade, L., Verbee, L.: 2014 Ebola Outbreak. Worldwide Air-Transportation, Relative Import Risk and Most Probable Spreading Routes.
  13. 13.
    Mekaru, S.: Ebola 2014: A Rapid Threat Assessment. The Disease Daily. (2014).
  14. 14.
    Poletto, C., Gomes, M.F. C., Pastore y Piontti, A., Rossi, L., Bioglio, L., Chao, D. L.,Longini, I. M., Halloran, M. E., Colizza, V., Vespignani, A.: Euro Surveill 19(42), 20936 (2014).
  15. 15.
    Tizzoni, M., Bajardi, P., Poletto, C., Ramasco, J.J., Balcan, D., et al.: BMC Med. 10, 165 (2012)CrossRefGoogle Scholar
  16. 16.
    Rvachev, L.A., Longini, I.M.: Math. Biosci. 75, 3–22 (1985)MathSciNetCrossRefGoogle Scholar
  17. 17.
    Flahault, A., Valleron, A.: Math. Popul. Stud. 3, 161–171 (1992)CrossRefGoogle Scholar
  18. 18.
    Colizza, V., Barrat, A., Barthelemy, M., Valleron, A.J., Vespignani, A.: PLOS Med. 4, e13 (2007)CrossRefGoogle Scholar
  19. 19.
    GPWv3: Gridded Population of the World. Socio Economic Data and Aplications Center at Columbia University (2014)Google Scholar
  20. 20.
    IATA: International Air Transport Association (2014)Google Scholar
  21. 21.
    OAG: Official Airline Guide (2014)Google Scholar
  22. 22.
    Simini, F., Gonzalez, M.C., Maritan, A., Barabasi, A.L.: Nature 484, 96–100 (2012)Google Scholar
  23. 23.
    Halloran, M.E., Longini, I.M., Struchiner, C.J.: Design and Analysis of Vaccine Studies, pp. 63–84. Springer Science + Business Media, New York (2009)Google Scholar
  24. 24.
    Diekmann, O., Heesterbeek, J.: Mathematical Epidemiology of Infectious Diseases: Model Building, Analysis and Interpretation. Wiley, Chichester (2000)zbMATHGoogle Scholar
  25. 25.
    van den Driessche, P., Watmough, J.: Math. Biosci. 180, 29–48 (2002)MathSciNetCrossRefGoogle Scholar
  26. 26.
    Bwaka, M., Bonnet, M., Calain, P., Colebunders, R., Roo, A.D., et al.: J. Infect. Dis. 179, S1–S7 (1999)CrossRefGoogle Scholar
  27. 27.
    Ndambi, R., Akamituna, P., Bonnet, M., Tukadila, A., MuyembeTamfum, J., et al.: J. Infect. Dis. 179, S8–S10 (1999)CrossRefGoogle Scholar
  28. 28.
    Dowell, S., Mukunu, R., Ksiazek, T., Khan, A., Rollin, P., et al.: J. Infect. Dis. 179, S87–S91 (1999)CrossRefGoogle Scholar
  29. 29.
    Khan, A., Tshioko, F., Heymann, D., Guenno, B.L., Nabeth, P., et al.: J. Infect. Dis. 179, S76–S86 (1999)CrossRefGoogle Scholar
  30. 30.
    Rowe, A., Bertolli, J., Khan, A., Mukunu, R., Muyembe-Tamfum, J., et al.: J. Infect. Dis. 179, S28–S35 (1999)Google Scholar
  31. 31.
    World Health Organization: Disease Outbreaks News.
  32. 32.
    Chowell, G., Hengartner, N., Castillo-Chavez, C., Fenimore, P., Hyman, J.: J. Theor. Biol. 229, 119–126 (2004)MathSciNetCrossRefGoogle Scholar
  33. 33.
    Ndanguza, D., Tchuenche, J.M., Haario, H.: Afr Mat 24, 55–68 (2011)MathSciNetCrossRefGoogle Scholar
  34. 34.
    WHO Ebola Response Team: N Engl J Med 371:1481–1495 (2014)Google Scholar
  35. 35.
    WHO Ebola Response Team: N. Engl. J. Med 372:584–587 (2015)Google Scholar
  36. 36.
    Weitz, J.S., Dushoff, J.: Sci. Rep. 5, 8751 (2015)Google Scholar
  37. 37.
    Gomes, M.F.C., Pastore y Piontti, A., Rossi, L., Chao, D., Longini, I., Halloran, M.E., Vespignani, A.: PLOS Currents Outbreaks, edn. 1. 2014 Sep 2. (2014). doi: 10.1371/currents.outbreaks.cd818f63d40e24aef769dda7df9e0da5
  38. 38.
    Merler, S., Ajelli, M., Fumanelli, L., Gomes, M.F.C., Pastore y Piontti, A., Rossi, L., Longini, I.Jr, Halloran, M.E., Vespignani, A.: Lancet Infect. Dis. 15(2), 204–211 (2015)Google Scholar

Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  • Ana Pastore-Piontti
    • 1
  • Qian Zhang
    • 1
  • Marcelo F. C. Gomes
    • 2
  • Luca Rossi
    • 3
  • Chiara Poletto
    • 4
  • Vittoria Colizza
    • 4
  • Dennis L. Chao
    • 5
  • Ira M. Longini
    • 6
  • M. Elizabeth Halloran
    • 7
  • Alessandro Vespignani
    • 1
    Email author
  1. 1.Northeastern UniversityBostonUSA
  2. 2.FiocruzRio de JaneiroBrazil
  3. 3.ISI FoundationTurinItaly
  4. 4.Sorbonne Universities, UPMC Univ Paris 06, UMR-S 1136, Institut Pierre Louis d’Epidemiologie et de Sante PubliqueParisFrance
  5. 5.Institute for Disease ModelingIntellectual VenturesBellevueUSA
  6. 6.Department of BiostatisticsUniversity of FloridaGainesvilleUSA
  7. 7.Fred Hutchinson Cancer Research CenterSeattleUSA

Personalised recommendations