Random Analytics: Ebola! (2013)
by Shane Granger
***** Please note that the infographics/charts of Ebola were updated with public source information to 12 July 2013 EST *****
I continue to remain morbidly fascinated by Ebola.
The World Health Organisation (WHO) states that EHF is a severe acute viral illness often characterized by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. Laboratory findings show low counts of white blood cells and platelets as well as elevated liver enzymes. People are infectious as long as their blood and secretions contain the virus. Ebola virus was isolated from seminal fluid up to the 61st day after the onset of illness in a laboratory acquired case. The incubation period (interval from infection to onset of symptoms) varies between 2 to 21 days. During EHF outbreaks, the case-fatality rate for the three fatal strains has varied from outbreak to outbreak between 24.8% and 89.5%.
Key Facts (issued August 2012 via the WHO):
- The Ebola virus causes severe viral haemorrhagic fever (VHF) outbreaks in humans.
- Viral haemorrhagic fever outbreaks have a case fatality rate of up to 90%.
- Ebola haemorrhagic fever 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.
- There is no treatment or vaccine available for either people or animals.
There were three outbreaks of EHF in 2012, two occurring in August and a later outbreak in November.
The first two were almost concurrent outbreaks, one of Ebola Sudan in Uganda and another of Ebola Bundibugyo in the Democratic Republic of Congo. The Uganda outbreak, in the Kibaale District would infect 24 and kill 17 including 12 members of the same family. The DRC outbreak, in the Province Orientale would eventually infect 77 and kill 36.
Barely a month after calling and end to Kibaale outbreak (and coincidentally an outbreak of Marburg) the Ugandan Ministry of Health had to deal with a second Ebola Sudan occurrence. The 2nd Ugandan outbreak, this time in the Luweero and Kampala Districts would infect seven and kill four.
As recently as late May 2013 it was thought that another outbreak had occurred in the DRC. Although there was an occurrence of some disease testing found that it was not EHF as noted by the CIDRAP News scan on the 4th June 2013.
There has also been some discussion about the possible progress in the fight against Ebola via an FDA research program in late June 2013 (a good abstract on this via H5N1) I thought it might be time to review one of my first WordPress articles, a piece on Ebola completed in October 2012.
Here is some spruced up analysis and analytics, including some updated data from the 2012 outbreaks in Uganda and the Democratic Republic of Congo.
The following infographic looks at some of the key dates and incidents in the history of the Ebola Haemorrhagic Fever (EHF). If you also want an idea of what the virus looks like I have included a photo of the disease under an electron micrograph (top right hand corner!).
Cases by Country and EHF strain
This infographic packs in a lot of information. First of all the circle sizes represent the amount of cases per country, split according to colour representing the four known strains of the disease. The known strains found in Africa are:
- EBOV: Ebola Zaire (or the Ebola Virus). Colour: Orange;
- SUDV: Ebola Sudan (or the Sudan Virus). Colour Green;
- BDBV: Ebola Bundibugyo (or the Bundibugyo Virus). Colour Violet;
- TAFV: Ebola Ivory Coast (or the Tai Forest Virus). Colour Brown.
Each country has additional details including total number of cases, fatalities and Case Fatality Rate (CFR).
It should be noted that I have not included a number of known laboratory incidents which have occurred outside of Africa and have resulted in at least one death (Koltsovo, Russia). I also have not included any details about the Ebola Reston which was exported in Philippine crab-eating macaque monkeys to the United States and Italy from 1989 through to 1992. Ebola Reston is not known to be dangerous to humans.
Note: I have created this infographic using Tableau Public software which can be viewed here.
CFR by Year and Strain
The final infographic looks at the Case Fatality Rates.
Each line represents a known occurrence of Ebola by onset year. If the outbreak has not completed within a calendar year the data is included from the date of the first onset. Thus the Dec 2008 – Feb 2009 Kasai-Occidental Ebola Zaire outbreak in the Democratic Republic of Congo which infected 32 and killed 15 is included as the 2008 EBOV line.
Although there have been no known outbreaks of EHF in 2013 it remains a highly visible reminder of our inability to completely dominate our natural space. Many other diseases infect, damage and kill more people but Ebola seems to have a special place in our high-speed mythology. No doubt this is due to its awful characteristics and super high case fatality rates. Amplification by movies such as Outbreak (made in 1995 but still watchable today) or by the writings of Tom Clancy and others who consistently turn the disease into a weapon adds to its macabre allure.
We are just a month away from August, the onset timings for both the opening 2012 outbreaks.
Will 2013 prove to be another deadly year?
Acknowledgements: The new and improved analysis could not have happened without Crawford Kilian and his H5N1 blog and the writings of Tara C. Smith (including her early work via Stanford University) but more recently her articles for National Geographic. Each disease I look at brings out a couple of new, highly specialised subject matter experts and Tara’s writings are excellent.