While the numbers surrounding the Ebola epidemic in West Africa are scary enough — the death toll is nearing 5,000, and a possible infection rate of 50,000 has been forecast — mutation, a single word, may be more worrisome than all of the virus's epidemiological statistics put together.
According to medical microbiologist Michael McCann, Ph.D., professor of biology and associate dean of the College of Arts and Sciences at Saint Joseph’s University in Philadelphia, there’s no question: The Ebola virus is mutating.
“Mutating is what an RNA virus, which is what Ebola is, does best,” McCann says.
RNA viruses — think influenza, HIV and the common cold — have a genetic base comprised of ribonucleic acid. These viruses are more prone to mutation because the mechanism that replicates the virus makes errors, or mutations, during the copying process.
McCann says that so far, Ebola mutations have not been remarkable. Different strains of the virus have been produced by mutations, but the strains are still transmitted through contact with bodily fluids, and the variants behave much the same way in each infected person. The pathogen enters the body through a break in the skin or another opening of the body. It then attacks the epithelial cells of the blood vessels, which lose their integrity throughout the body, causing hemorrhages.
But if Ebola is an RNA virus, like the rhinovirus, (the virus that causes the common cold), can its constant mutations change it enough so that it could become airborne, like the cold virus?
McCann says there is no evidence that an infected person who is coughing will produce aerosol droplets containing virus particles that can cause infection.
“The kinds of changes that would have to occur for Ebola to transform from a bodily fluid transmission to a respiratory transmission are not trivial,” McCann notes. “This would require substantial changes in the receptors of the virus for it to be successful attaching to and infecting respiratory epithelial cells.”
The bigger issues relating to the mutating Ebola virus concern the development of a viable vaccine, according to McCann.
“A vaccine triggers an immune response against a particular set of viral proteins,” McCann notes. “But with a frequently mutating virus like Ebola, it’s possible that medical science could produce a vaccine against a specific Ebola strain that then mutates, and that vaccine may or may not induce protective immunity against the variant.”
In addition, McCann says the mutations could cause problems with Ebola diagnostic tests, many of which are antibody-based.
“The antibodies bind to a particular surface protein,” says McCann. “If there are enough mutations in that surface protein, the virus could change so that some strains of it might not show up on the test, and we could have a situation where the current diagnostic tools wouldn’t capture all of the virus variants. Some Ebola cases could go undetected until the person develops more severe symptoms, which could complicate treatment and the prevention of additional infections.”
McCann can be reached for comment at 610-660-1823, at [email protected], or by calling University Communications at 610-660-3240.
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