Ruminations

Is Ebola Evolving?

And yet, at home in the U.S. and in other non-African nations, our doctors seem more concerned with the flu. They urge us to get our shots each year, remind us to wash our hands, stress the importance of staying home if we're sick. Though the WHO declared the ebola epidemic a global health emergency, it is widely accepted that the disease's threat is limited in Western nations, which have more robust public health infrastructures that boast they can easily contain any individual(s) harboring the disease so that it cannot spread.

This is in part because it is reasonably difficult to acquire the disease, as you must have the bodily fluids of an infected person land on your body's mucosa (i.e. in your nose, ears, genital areas, anus, or eyelids or lips). The flu, by contrast, is airborne, and you need only share airspace with an infected person to contract the disease yourself. 

The ebola epidemic is particularly dire in Liberia, Sierra Leone, and Guinea because of those nation's respective environments: they are all impoverished, lack basic infrastructure, and increasingly view health care workers as responsible for the spread of ebola, not its treatment. Finally, regional funeral practices require close contact with the deceased's body, bringing healthy family members close to the hazardous bodily fluids of the dead. 

For these reasons, the U.S. government feels confident in its abilities to protect American citizens from the disease. This confidence is further boosted by the recent announcement of the ebola vaccine, which is currently being tested on a few American health care workers who contracted the disease while in West Africa and have returned home for treatment. (It should be noted that the vaccine's efficacy is indeterminate, and that the number of vaccines available is essentially zero, though production is quickly increasing.) 

However, there is concern, backed by millions of years of evolutionary history, that the ebola virus has the potential to evolve into a less virulent, but much more easily (and rapidly) spread strain. Currently, the virus is so virulent that it quickly runs out of hosts, because it kills them off faster than it can be spread. This is the likely explanation for the short run of the virus in previous east African outbreaks -- if everyone infected is getting terrible symptoms that leave them bedridden and, shortly, dead, then there is no one to continue transmitting the virus. 

But if the virus were able to decrease it's virulence so that infected people can walk around and spread the disease before they even know they are sick, or if their sickness doesn't feel so severe that those harboring the disease keep up with work and maintain some semblance of a social life, then the virus can reach many people. Essentially, ebola could mutate to mimic the common flu, letting its hosts spread the virus to an infinite number of people before striking. In this situation, the virus might only be able to kill 3 out of 10 people, but if millions of people are infected, 3 out of 10 is suddenly a very big number. (This fear is made all too real when one considers the hyper-connectivity of the world today, with its innumerable plans, trains, and automobiles.) 

The question is whether or not ebola is currently in a situation to mutate into a less virulent form. Though we can speculate knowledgeably based on the conditions in which other viruses have mutated in the past, we will not have a definitive answer to this question for months, or even years. Additionally, the nature of this potential mutation -- whether it will render itself impotent, or whether it will maintain its ferocity but be able to spread across the globe -- will likewise remain a mystery, until the answer reveals itself to us, perhaps softly, or perhaps with a great big boom. 

For more information on this topic, I recommend reading the works of the father of evolutionary virulence theory, Paul Ewald. His 1993 paper "The Evolution of Virulence" helped to shape this post. 

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