In an fascinating rebuttal of a column by CIDRAP director, Michael Osterholm, PhD, one virology professor writes, “The likelihood that Ebola virus will go airborne is so remote that we should not use it to frighten people. We need to focus on stopping the epidemic, which in itself is a huge job.”
In response to Dr. Osterholm’s New York Times OpEd entitled What We’re Afraid to Say About Ebola, Columbia University Professor of Immunology and Microbiology, Vincent Racaniello, PhD posted his thoughts on the “Ebola going airborne” scenario on his website, Virology Blog Thursday.
The post entitled, What we are not afraid to say about Ebola virus, Dr. Racaniello notes after a a discussion of viral mutation in RNA viruses, “The more hosts infected by a virus, the more mutations will arise. Not all of these mutations will find their way into infectious virus particles because they cause lethal defects. But Osterholm’s statement that the evolution of Ebola virus is ‘unprecedented’ is simply not correct. It is only what we know. The virus was only discovered to infect humans in 1976, but it surely infected humans long before that. Furthermore, the virus has been replicating, probably for millions of years, in an animal reservoir, possibly bats. There has been ample opportunity for the virus to undergo mutation.”
Racaniello continues to say–More problematic is Osterholm’s assumption that mutation of Ebola virus will give rise to viruses that can transmit via the airborne route:
If certain mutations occurred, it would mean that just breathing would put one at risk of contracting Ebola. Infections could spread quickly to every part of the globe, as the H1N1 influenza virus did in 2009, after its birth in Mexico.
The key phrase here is ‘certain mutations’. We simply don’t know how many mutations, in which viral genes, would be necessary to enable airborne transmission of Ebola virus, or if such mutations would even be compatible with the ability of the virus to propagate. What allows a virus to be transmitted through the air has until recently been unknown. We can’t simply compare viruses that do transmit via aerosols (e.g. influenza virus) with viruses that do not (e.g. HIV-1) because they are too different to allow meaningful conclusions.
Using HIV-1 and hepatitis C as two of many possible examples, Racaniello writes:
When it comes to viruses, it is always difficult to predict what they can or cannot do. It is instructive, however, to see what viruses have done in the past, and use that information to guide our thinking. Therefore we can ask: has any human virus ever changed its mode of transmission?
The answer is no. We have been studying viruses for over 100 years, and we’ve never seen a human virus change the way it is transmitted.
There is no reason to believe that Ebola virus is any different from any of the viruses that infect humans and have not changed the way that they are spread.