Ebola for Dummies

I don't want to brag, but I have access to the internet pretty much 100% of the time nowadays, and so very occasionally I glance at some of the news websites. There seems to be quite a lot of column inches dedicated to the ongoing West African Ebola Epidemic, and perhaps rightly so since if the news articles are to be believed this virus is proving to be a fairly destructive problem. Fear-mongers hypothesise that this is the beginning of the apocalypse. I’ve seen Outbreak and Contagion, so maybe they’ve got a point? Embarrassingly for a so-called medical student I knew almost nothing about this important disease, so I’ve now spent a few hours reading about it using my aforementioned internet access. And because I haven’t written anything on this blog since my elective I’ll write down what I found out here.

Ebola haemorrhagic fever is caused by the Ebola virus (EBOV) first isolated in 1976: usually an 800nm tubular protein mesh covered in a lipid bilayer and containing a single strand of RNA which codes for 288 amino acids as eight proteins. It is impressive that such a tiny and relatively simple bag of molecules is responsible for the miserable disease – as of the beginning of august over 1600 cases and 887 deaths have been reported to the WHO.

Electron micrograph of an ebola virion

Ebola haemorrhagic fever is also known as Ebola Virus Disease (EVD) and is one of the most virulent viral diseases in the world. It is named for the Ebola river in the Democratic republic of Congo (then Zaire), where the first cases were recorded. The virus is first acquired upon contact with bodily fluids from an infected animal, usually from handling infected wild animal carcasses – including primates hunted for bushmeat. Bats are thought to be the reservoir species for the ebola virus, from which apes and other wild and domestic animals can become infected – the virus is a zoonosis.

A CDC graphic from http://www.cdc.gov/vhf/ebola/resources/virus-ecology.html

Like seemingly every other disease in the world, the disease first presents as a “flu-like” stage due to the inflammatory reaction to viral particles and cell debris . These general symptoms appear about a week after contraction of the virus, and the early fever mimics other more common tropical fevers such as malaria or dengue. However, EVD becomes more severe as the virus produces a glycoprotein that binds to the interior surface of blood vessels and significant bleeding – seen as haematemesis (vomiting blood), petechiae and purpura (bleeding into the skin), as well as bleeding from elsewhere such as the eyes, nose, gums, GI tract etc.

The mortality rate can be as high as 90% as organs fail, though I imagine this number is highly variable depending on the strain of the pathogen, accuracy of diagnosis and promptness and effectiveness of (supportive) treatment. There is no specific treatment and no available vaccine but survival is increased with early interventions such as balancing fluids, electrolytes and coagulation and treating secondary infections.

Now

Since March 2014 in Guinea, West Africa, there has been an ongoing epidemic of this disease – and the most severe outbreak ever recorded, caused by the most dangerous strain, Zaire ebolavirus. The strain has since spread to neighbouring Sierra Leone and Liberia. As of today, August 4th, here have been no cases outside of Africa, though (worryingly?) two infected Americans have been flown to the states for treatment.

WHO epidemic figures up to August 1st

So far, the total number of deaths from the disease is still low, and whilst each case is individually horrific the overall disease burden is insignificant when compared with influenza or TB or HIV or malaria or any one of hundreds of others. Further, compared to other pandemic scares like SARS or bird flu, after five months the virus is fortunately yet to deliver the global chaos that some have predicted.