Assessment of the Risk of Ebola Virus Transmission from Bodily Fluids and Fomites (From Discussion)
There was a significant discrepancy between the results of virus culture and RT-PCR testing in our study, with many more frequent positive results from RT-PCR. Possible explanations for this finding include virus degradation from breaks in the cold chain during sample collection, storage, and shipping; the greater sensitivity of RT-PCR relative to culture; and, in the case of the saliva specimens, possible virus inactivation by salivary enzymes. The less-than-ideal storage conditions of the specimens in the isolation ward immediately after acquisition and the fact that even the nasal blood from 1 patient was culture negative suggest that some virus degradation indeed occurred. Nevertheless, we cannot exclude the possibility of a true absence of viable virus in the original samples. We hope to be able to repeat this study in the future with better maintenance of the cold chain to resolve this question.
Given that the nasal blood of an infected individual in the midst of clinical symptoms came up negative on culture, this study has a significant problem that the authors noted. Use of this study to make claims regarding transmission without the accompanying qualifier isn't particularly good practice IMO, especially when used to claim that a particular vector is impossible/improbable.
I think the RT-PCR test results are the significant portion of this specific study given the issues surrounding the sample handling.
In a previous post (number 2118) you wrote:
In order for Ebola to become airborne, it would have to 1) infect cells in the upper respiratory system, in the bronchia and possibly alveoli, and 2) be resistant to destruction by drying.
Ebola infects dendritic cells, which are numerous in the respiratory tract. Additionally, the virus has demonstrated very wide tropism in animal models and human samples. Please provide a source for the claim that other respiratory cells are not currently subject to infection and "must" be infected in order for airborne (medical definition) transmission to occur. As far as I am aware, the various cell types of the human respiratory tract are not exempt from Ebola infection.
While the article said that there wasn’t much risk of Ebola slime infection unless their was blood involved, however, see the following admission from that article —
Nevertheless, we cannot exclude the possibility of a true absence of viable virus in
the original samples. We hope to be able to repeat this study in the future with
better maintenance of the cold chain to resolve this question.”
The 2007 test team’s samples _ran out of liquid nitrogen cooling_ for their Ebola samples between Africa and its virus culture testing by the CDC in Atlanta.
Which, given the infection rates we are seeing in Liberia and elsewhere, means the samples went bad in transit due to the coolent break in the transportation chain.
The bottom line is we still don’t know the human infection rate from non-blood based human body fluids in the environment.
In my personal experience, it is quite possible to find virus by RT-PCR that simply cannot be confirmed by plaque assay. All RT-PCR does is tell you that large enough fragments of viral RNA exist to give a positive result on the PCR test. It tells you nothing about virus viability.
The study described in that J. Inf. Disease article was less-than-ideal for a number of reasons. Were I a reviewer of that paper, and the virus anything but Ebola, I would not have recommended its publication. Probably whoever reviewed it thought the same.
In a previous post (number 2118) you wrote:
In order for Ebola to become airborne, it would have to 1) infect cells in the upper respiratory system, in the bronchia and possibly alveoli, and 2) be resistant to destruction by drying.
Ebola infects dendritic cells, which are numerous in the respiratory tract.
The airborne viruses I know all infect ciliated epithelial cells in the upper respiratory tract. The last time I checked, dendritic cells are not ciliated. The virus would also have to change its physical structure in order to become airborne, to make it resistant to drying. Right now, the virus spreads just fine through infected fluids and possibly droplet transmission--there is no selective pressure for it to change mode of transmission.
I do not know of any Ebola researchers who think that Ebola is airborne, or that it spreads through means other than close contact or proximity with infected persons. If you can provide examples of actual research papers, peer-reviewed and indexed in PubMed, that definitively demonstrate true airborne (NOT droplet, NOT fomite) transmission of Ebola from a human--or even non-human primate--please post the reference(s). Otherwise, quit trying to find ways to make the evidence fit your desire for Ebola to be airborne. It is not, and no knowledgeable person has ever said otherwise.
FYI, here is a nice article from Scientific American that explains why Ebola is not airborne and is not likely to become airborne. It is written for consumption by laypeople, and seems to avoid the dense language that scientists such as myself often use.
The next time influenza sweeps around the northern hemisphere, seemingly simultaneously across the whole hemisphere, you might want to get down on your knees and thank God that Ebola is not airborne. Influenza season is coming, and there is nothing we can do to stop its spread.