...interviews with several infectious diseases experts reveal that whereas such a mutationor more likely series of mutationsmight physically be possible, its highly unlikely. In fact, theres almost no historical precedent for any virus to change its basic mode of transmission so radically. We have so many problems with Ebola, lets not make another one that, of course, is theoretically possible but is pretty way down on the list of likely issues," says infectious diseases expert William Schaffner of Vanderbilt University. "Everything that is happening now can easily be comprehensively explained by person-to-person spread via body contact. We dont have to invoke anything e
lse.
Here is what it would take for it to become a real airborne risk: First off, a substantial amount of Ebola virus would need to start replicating in cells that reside in the throat, the bronchial tubes and possibly in the lungs. Second, the airborne method would have to be so much more efficient than the current extremely efficient means of transmission that it would overcome any genetic costs to the virus stemming from the mutation itself. Substantial natural hurdles make it unlikely that either event will occur.
Ebola typically gains entry into the body through breaks in the skin, the watery fluid around the eye or the moist tissues of the nose or mouth. Then it infects various cells of the immune system, which it tricks into making more copies of itself. The end result: a massive attack on the blood vessels, not the respiratory system.
Even viruses that are well adapted to attacking the respiratory system often have a hard time getting transmitted through the airways. Consider the experience so far with avian flu, which is easily transmitted through the air in birds but hasnt yet mutated to become easily spreadable in that fashion among people.
The difficulty is that those [flu] viruses dont have the protein attachments that can actually attach to cells in the upper airway. They have to develop attachments to do that, Schaffner says. So even if a virus were exhaled, it would need to lodge onto something in another persons cells that are already prepared for it in the upper airway. Since the virus doesnt have attachment factors that can work in the upper airway, its very rare for it to go human to human, and then it almost always stops and doesnt get to a third person,
he delicate lock-and-key proteinvirus fit required for the virus to successfully latch onto and replicate in the airway has not developed because there is no evolutionary pressure for it to do so; it simply would not be an efficient option.
http://www.scientificamerican.com/article/fact-or-fiction-the-ebola-virus-will-go-airborne/
