Thursday, October 02, 2014

Mackay On Ebola `Direct Contact’ & Droplet Transmission



# 9142


Dr. Ian Mackay once again takes on the subtleties of Ebola transmission on his excellent VDU blog today, and brings a new level of clarity.   As he and I have discussed before (see VDU Blog: Droplets vs Airborne - Demystifying Ebola Transmission), Ebola isn’t an `airborne’ virus – but you can be infected via droplets emanating from an infected individual.

What I’ve dubbed `spittle range’ where large droplets of mucus, blood, sweat, or other bodily fluids could potentially be coughed, sneezed, or otherwise propelled or flung onto another person.  


Last Month, in Ebola: Parsing The CDC’s Low Risk vs High Risk Exposures, we looked at CDC guidance that acknowledged the (low) risks of casual contact; defined as spending a prolonged period of time in the same room with, or within 1 meter, of an infected patient – even without direct physical contact.



In the light of all of this, the heavily parsed and highly promoted meme -  that `You can’t get Ebola through air’  -  tends to cause more confusion than reassurance.


To the rescue today comes Dr. Mackay, who explains what `direct contact’  really means.  I’ve only included a snippet, follow the link to read:



It's what falls out of the aerosol that matters....


Direct contact.

When we talk about "direct contact" and Ebola virus transmission, we do include the bigger wetter heavier droplets that might be propelled from of a sick person during vomiting, or coughing as a risk for transmitting virus.

Even though that is not physical direct contact, and even though the droplets travel across a gap between people - through the air - it is still a direct line from person A (red in the graphic below) to B (blue). If B is too far away, then those droplets fall to the ground before they hit B. The droplets may remain infectious on the ground. That depends on temperature, humidity, surface type and the type and amount of virus.

(continue . . . .)

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