Random Analytics: Top 10 Ebola Outbreaks by Case Numbers (to 11 Apr 2014)

by Shane Granger


“This is one of the most challenging Ebola outbreaks that we have ever faced. And the reasons why this is one of the most challenging outbreaks is that, first we see a wide geographic dispersion of cases. So this has come in from a number of districts as well as a large city in Guinea, Conakry.” Dr Keiji Fukuda, WHO (10 April 2014).

The latest outbreak of Ebola Zaire, which is ongoing, has now infected 157-persons and taken the lives of 101 in Guinea while in neighbouring Liberia up to 25-persons have been infected with 12-deaths. As I write this post there are unconfirmed reports of the outbreak spreading to Mali while other countries have been ruling out cases through intensive testing. Both outbreaks are fluid and those numbers may increase or decrease as data solidifies or the virus spreads further. See the latest World Health Organisation (WHO) Disease Outbreak News (DON) from the two countries (correct as at 10 April 2014) for the latest details.

As part of a post-graduate program I am undertaking to build a five-minute Ebola Virus Disease lesson utilising just five graphs and six-dot points (as supplied by the WHO). Here is the latest chart along with previous chart(s) and my dot-points:

New Chart – Ebola (Top 10 Outbreaks by Case Numbers)

02 - Ebola_CasesbyClassYear_140411

***** Please note that this infographic of the EVD was updated with public source information to 0800hrs 11 April 2014 (EST). *****

The next infographic addition displays the top 10 outbreaks in order of case numbers and each horizontal bar is filled with the flag of the country where the outbreak occurred. With confirmed/suspected cases in Guinea (157) and Liberia (25) for a total of 182 the outbreak (coded EBOV17) has now become sixth largest based on case numbers. The largest outbreak (SUDV4) was of Ebola Sudan in Uganda (2000) when 425 became infected and 224 died. The only other recording of an EVD that jumped borders prior to this was in the 10th worst outbreak (EBOV8) when a doctor caught the disease in Gabon and subsequently travelled on a plane to South Africa where he infected health care workers.

Notes: In order from lowest to highest. 10th: EBOV8 (Gabon/South Africa), 9th: EBOV9 (Gabon), 8th: EBOV11 (Republic of Congo), 7th: BDBV01 (Uganda), 6th: EBOV17 (Guinea/Liberia), 5th: EBOV15 (Democratic Republic of Congo), 4th: SUDV1 (technically Sudan but would now be South Sudan), 3rd: EBOV6 (Zaire but now the DRC), 2nd: EBOV2 (Zaire but now the DRC) and 1st: SUDV4 (Uganda).

Chart 2 – Ebola (Cases by Classification and Year) * UPDATED *

01 - Ebola_Top10OutbreaksByCaseNo_140411

***** Please note that this infographic of the EVD was updated with public source information to 0800hrs 11 April 2014 (EST) *****

The updated infographic shows cases by classification (Ebola Zaire, Sudan, Bundibugyo, Reston and Ivory Coast) by year and then split into those recovered or those deceased (following in a red variant). As you can see the initial outbreak of the both Ebola Zaire and Sudan in 1976 was the most significant with 603 cases and 431 deaths (a combined Case Fatality Rate of 71.5%). With up to 182 confirmed cases so far the 2014 outbreak numbers are already fifth in terms of case numbers.

Notes: Several years had just one case. They are 1972 (a retrospective fatality of Ebola Zaire in Zaire), 1977 (a single case of Ebola Zaire in Zaire), 1988 (an accidental infection of Ebola Zaire in Porton Down, UK) and 2011 (a single fatality of Ebola Sudan in Uganda). The 2014 numbers are currently provisional.

Key Facts: (source: Fact Sheet 103, WHO, last updated March 2014)

  • The Ebola virus causes Ebola virus disease (EVD; formerly known as Ebola haemorrhagic fever) in humans;
  • EVD outbreaks have a case fatality rate of up to 90%;
  • EVD outbreaks occur primarily in remote villages in Central and West Africa, near tropical rainforests;
  • The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission;
  • Fruit bats of the Pteropodidae family are considered to be the natural host of the Ebola virus;
  • No specific treatment or vaccine is available for use in people or animals.

Acknowledgements:Data for this infographic was sourced from official reports from the World Health Organisation. I have also utilised resources from the CDC, CIDRAP, H5N1, Virology Down Under and National Geographic.