With nurses coming down with Ebola in both Dallas and Madrid hospitals, despite being fully suited up, it’s beginning to rather look as if insufficient precautions have been taken.
Most of the blame is being laid on the nurses themselves, for not following strict procedures – although neither nurse seems to have any clear recollection of doing things the wrong way.
Now, via ZeroHedge, a new claim is being made by CIDRAP:
The Center for Infectious Disease Research and Policy (CIDRAP) is a global leader in addressing public health preparedness and emerging infectious disease response. Founded in 2001, CIDRAP is part of the Academic Health Center at the University of Minnesota.
And they’re saying:
We believe there is scientific and epidemiologic evidence that Ebola virus has the potential to be transmitted via infectious aerosol particles both near and at a distance from infected patients, which means that healthcare workers should be wearing respirators, not facemasks.
At the moment the medical orthodoxy is that Ebola is only transmitted by coming into physical contact with body fluids. To which CIDRAP responds;
This reflects an incorrect and outmoded understanding of infectious aerosols, which has been institutionalized in policies, language, culture, and approaches to infection control. We will address this below. Briefly, however, the important points are that virus-laden bodily fluids may be aerosolized and inhaled while a person is in proximity to an infectious person and that a wide range of particle sizes can be inhaled and deposited throughout the respiratory tract.
The reason that aerosols are usually rejected as a transmission medium is because very small droplets ( < 5 μm) are believed to evaporate almost immediately. However, CIDRAP says:
Experimental work has shown that Marburg and Ebola viruses can be isolated from sera and tissue culture medium at room temperature for up to 46 days, but at room temperature no virus was recovered from glass, metal, or plastic surfaces. Aerosolized (1-3 mcm) Marburg, Ebola, and Reston viruses, at 50% to 55% relative humidity and 72°F, had biological decay rates of 3.04%, 3.06%. and 1.55% per minute, respectively. These rates indicate that 99% loss in aerosol infectivity would occur in 93, 104, and 162 minutes, respectively.
In still air, 3-mcm particles can take up to an hour to settle. With air currents, these and smaller particles can be transported considerable distances before they are deposited on a surface.
So infective aerosols can float around in air at room temperature for 2 or 3 hours, they say.
This strikes me as being entirely plausible. As I understand it, an aerosol particle won’t evaporate if it’s floating in 100% humid air. And in Monrovia, Liberia, air humidity quite often approaches 100% relative humidity (as I can remember from the times I sat in its airport, waiting for my plane to be re-fuelled).
And today, as a matter of interest, I found out how big Ebola virus particles are (970 nm long, 80 nm round) and worked out how many could fit into a 0.05 ml drop of water, and a 5 μm aerosol droplet. My back-of-envelope calculations gave a maximum 8000 billion in a drop of water, and 20,000 in an aerosol droplet (although actual values would undoubtedly be very much less).
However, since none of the friends and family of the Madrid and Dallas Ebola patients seem to have shown any symptoms as yet, it rather looks as if you need to get a very large dose of virus particles before you contract Ebola. And it’s mostly hospital nurses attending dying Ebola patients who would be in the kind of environments where there are very large quantities of the virus present. And they should be provided with the maximum possible protection, particularly with a disease with which they have little or no experience.
Also, since in Liberia something like 40% of the population seems to be immune to Ebola, it rather suggests that very low doses of Ebola may be sufficient to stimulate the immune system to produce antibodies against it, and provide immunity.
So as long as Ebola victims are quickly identified and isolated, and their nursing staff given maximum protection (which they don’t seem to be getting yet), it ought to be quite easy to contain any Ebola outbreak.
And then they can go back to their “tobacco epidemic”. Or can they?