The evolution of Ebola
Could Ebola evolve and become an even greater threat to humankind?
It can be transmitted between people via body fluids, which makes it easier to control – but if it evolved airborne transmission, it could become a much greater global threat. How likely is that to happen?
Ebola, like many viruses, is evolving rapidly – partly because mistakes are common when its genome is being copied and partly because viruses reproduce very rapidly.
In humans, Ebola virus evolution seems to have accelerated still further. This may be because particular forms of the virus are adapted to its natural host and tend to predominate, but many forms are able to thrive in a new host lacking effective defence mechanisms.
The future evolution of Ebola is hard to predict. Natural selection will not inevitably lead to increasing severity of a disease. Although dengue virus is evolving in ways that cause more serious disease, other viruses have evolved to become more benign – not killing your host is a good way of surviving longer and reproducing more over the long term. Indeed, the relationship with some viruses is so close that they have become integrated into the host genome (although generally they no longer reproduce as viruses).
However, although viruses evolve extremely rapidly, a switch from body fluid-based to airborne transmission is a big biological leap.
The Ebola family of viruses is thought to have been around for thousands of years, but there is no evidence that any have evolved to be transmitted in this way. Virus particles would have to evolve to survive outside the body and become resistant to drying. In addition, viruses spread through the air typically affect the lungs, whereas Ebola prefers internal organs such as the liver.
So could Ebola evolve to go airborne? It’s not impossible, but it is unlikely as things stand.Lead image:
Maurizio de Angelis/Wellcome Images CC BY NC ND