Ebola: The Good, The Bad, and The Gorillas

By now you have probably heard that there is a massive outbreak of Ebola virus going on in West Africa. Even if you have been living under a rock somewhere in the jungle it is likely that Ebola is on your radar, partially because that is where Ebola tends to hide out. As we head into the sixth month since the outbreak began, it is even starting to worry people far outside Africa, as infected people are transferred to facilities throughout Europe and North America for treatment, potentially exposing millions of more people to the disease. But before we all barricade ourselves in our bomb shelters, it is important that we understand what is actually going on.

The media tends to exaggerate things. As we all know, getting good ratings is often even more motivating than telling an accurate story. With that in mind, it is important to take a look at the science behind Ebola.

Unfortunately, one thing the media has gotten right is that Ebola virus disease is fantastically fatal to humans. As we learned back in Sketchy Fact#47, rabies is the deadliest virus on the planet with a 99.999% fatality rate. Ebola is one of the few viruses that plays in that same ballpark. There are 5 different species of Ebola virus and each has its own potency. Reston Ebolavirus is the least dangerous to people, with zero fatalities (you really don’t want Reston if you’re a macaque, however). Sudan Ebolavirus is the middle of the pack killer, with a fatality rate between 50 and 60%. The really scary form of the virus is Zaire Eboloavirus, with a historical fatality rate of around 90%. The really bad news? The current outbreak is the Babe Ruth of Ebola.

Ebola is named after the Ebola River in the Democratic Republic of Congo, near the location of one of the first ever outbreaks and now possibly the least desired honeymoon spot on the planet. First discovered in 1976, Ebola is a relatively new scourge on the super-deadly disease circuit. Since the first few small outbreaks in the 70’s the virus has popped up sporadically, all but disappearing until a string of fatal outbreaks in the mid 90’s. However, nothing compares to the current outbreak. Before 2014 the deadliest ever Ebola outbreak occurred in 1976 and killed 280 people. So far this year, over 2,000 people have died.

Ebola is so deadly because of the way it spreads through the body, actually using a person’s own immune system against them. When the virus infiltrates a cell it takes over the cell’s ability to reproduce DNA, hijacking it to make copies of its own genetic code. Ebola is an RNA virus, meaning that instead of the double helix DNA ladder we are all used to, there is only one strand to be copied. This makes the process fast and fierce. Once the cell is overwhelmed with virus is bursts and the immune system kicks in.

The immune system sends out cells called cytokines to attack the virus. However, where most viruses are overwhelmed like a physics major on a date with a cheerleader at the mere site of a cytokine, Ebola has the charisma of George Clooney. Rather than being destroyed by the cytokines, the virus hitches a ride and uses them to spread around the body into the tissue that makes up the walls of blood vessels. Ebola next attacks the liver, killing more cells and stopping the immune system's alarm chemicals from being cleared from the blood. The result is that the immune system keeps sending out troops and Ebola keeps bringing them over to the dark side. The outward symptoms resemble a really terrible flu including fever, vomiting, and diarrhea. The latter two symptoms including the presence of blood in the later stages or the disease.

As the virus eats away at the circulatory system blood clots form all over the body, clogging arterties. Eventually organs begin to shut down and blood vessels rupture causing massive internal bleeding. Contrary to popular belief, and in opposition to what the historic misnomer “Ebola Hemorrhagic Fever” would lead you to believe, most patients don’t bleed externally. Instead bruises form as blood escapes vessels within the body. Most people don't die of blood loss, however; it is organ failure that gets them. Ebola can kill you within 7 days of getting into your body.

This is all rather terrifying news, but there is hope. Ebola is spread by contact with bodily fluids, so to become infected you need to be closely caring for, or intimately interacting with, an infected person. The reason the virus has been able to spread so effectively in Africa is that local customs in rural villages at the centre of the outbreak involve close contact with the bodies of recently dead family members. On top of that, the health care system in many African countries just isn't equipped to contain an epidemic. Another deeply uncomforting reason the virus isn’t likely to cause a global pandemic is that it kills people very quickly, leaving it little chance to infect new hosts.

Ebola, like rabies, is thought to use bats as its natural reservoir. It lives in peace causing no trouble to the bat or anyone else under normal circumstances. The problem, or “spillover,” occurs when people eat the bats as bush meat or when another animal, say a gorilla, stumbles upon a piece of fruit that an infected bat was recently gnawing on. In fact, Ebola is as scary for gorillas as it is for people. It is thought that since 2000 Ebola has killed over 5000 gorillas in central Africa, severely damaging an already threatened population.

So there it is, the truth about Ebola. Here’s hoping that the effected countries are able to educate people soon enough to stop the current outbreak before the death toll gets much higher. From there we can worry about educating the gorillas.

References:

http://www.sciencemag.org/content/314/5805/1564.short

http://www.who.int/mediacentre/factsheets/fs103/en/

http://www.webmd.com/a-to-z-guides/ebola-fever-virus-infection

http://www.nature.com/nature/journal/v438/n7068/abs/438575a.html

http://www.sciencedirect.com/science/article/pii/014067369090737P

http://www.nature.com/nature/journal/v408/n6812/abs/408605a0.html

http://www.cdc.gov/vhf/ebola/outbreaks/guinea/

http://www.thehealthsite.com/news/ebola-virus-disease-how-does-the-virus-kill/

http://io9.com/a-chart-showing-the-history-of-ebola-outbreaks-in-the-w-1627422358