Showing posts with label Droplet. Show all posts
Showing posts with label Droplet. Show all posts

Friday, October 31, 2014

The Return Of The CDC’s `How Ebola Spreads’ Infographic

image

Droplet Spread – Credit CDC

 

# 9273

 


Earlier today I mentioned that an infographic showing that Ebola can potentially spread over short distances via droplets had been temporarily pulled by the CDC, just 5 days after first releasing it (see Guidance Gone, But Not Forgotten).   Since this removal was causing such a stir online and in the media, I expressed hopes it would be reinstated soon.

 

Well, I am very pleased to say that a slightly modified (and not in a bad way) version of the original poster has now been uploaded to the CDC’s website (PDF LINK).

 

The central messages remain the same.  Ebola isn’t an airborne virus – but it can potentially be spread over short distance via droplets propelled by coughs or sneezes.   Exactly why it was deemed necessary to pull the old version escapes me, but I am happy to see the information back online.


Kudos to the CDC for getting this done.

 

 

simage

Saturday, October 25, 2014

CDC: Ebola May Be Spread By Droplets, But Is Not Airborne

image

 

 

# 9250

 

Over the past few months Dr. Ian Mackay and others (including this humble blogger) have taken pains to explain that Ebola is not an `airborne virus’, but that it can be spread over short distances via large droplets that might be coughed, sneezed, or otherwise propelled from an infectious patient.   

 

Some of Ian’s efforts include:

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

The wind beneath my Ebola virus....

 

What I’ve often referred to as being within `spittle range’  (see Ebola Risk Communications & Ebola: Parsing The CDC’s Low Risk vs High Risk Exposures).  

image

 

The CDC’s initial meme (see above) – that `You can’t get Ebola through Air’ – while technically true –  I felt was lacking in that it never quite spelled out the potential risks of droplet transmission. 

 

Which is why I’m very pleased to see the following, far more informative graphic appear on the CDC’s Ebola website yesterday.

 

image

Thursday, October 02, 2014

Mackay On Ebola `Direct Contact’ & Droplet Transmission

image

 

# 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.

 

image

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....

(Excerpt)

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 . . . .)

Saturday, August 16, 2014

VDU Blog: Droplets vs Airborne - Demystifying Ebola Transmission

image

Except from CDC Infographic

 

 

# 8962

 

Almost two weeks ago the CDC released a reassuring infographic (see above) that - among other things - stated that `You can’t get Ebola through Air’, which immediately set off an internet firestorm of disbelief and derision. I considered it a communications misstep at the time, and blogged about it in The Ebola Sound Bite & The Fury.

 

While I understand the need to reassure the public, and the desire to try to defuse some of more egregious tabloid-style reporting, sometimes reassurance can be overdone.

 

When people see moon-suited doctors ferrying Ebola patients into Emory University Hospital, and compare that to the CDC’s blanket assurance that `You can’t get Ebola through the Air’  – they rightfully come away confused, and perhaps even a bit suspicious.

 

Last week, 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. 

 

What I 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.  

 

Today, I’m very pleased to report that Dr. Ian Mackay (along with three other researchers) – all far more qualified to weigh in on this subject than I  – have penned a detailed essay on what we know about Ebola transmission, which will hopefully clear up some of the confusion.  

 


Follow the link to read:

 

Ebola virus may be spread by droplets, but not by an airborne route: what that means

An article collaboratively written by (alphabetically)..

Dr. Katherine Arden
A postdoctoral researcher with interests in the detection, culture, characterization and epidemiology of respiratory viruses.

Dr Graham Johnson
A post-doctoral scientist with extensive experience investigating respiratory bioaerosol production and transport during breathing, speech and coughing and determining the physical characteristics of these aerosols.

Dr. Luke Knibbs
A Lecturer in Environmental Health at the University of Queensland. He is interested in airborne pathogen transmission and holds an NHMRC Early Career Fellowship in this area.

A. Prof Ian Mackay
A virologist with interest in everything viral but especially respiratory, gastrointestinal and central nervous system viruses of humans.

________________________

The flight of the aerosol

Understanding what we mean when we discuss airborne virus infection risk


A variant Ebola virus belonging to Zaire ebolavirus (EBOV) is active in four West African countries right now. Much is being said and written about it, and much of that revolves around our movie-influenced idea of an easily spread, airborne horror virus. Many people worry about their risks of catching EBOV, particularly since it hopped on a plane to Nigeria. However, all evidence suggests that this variant is not airborne. The most frequent routes to acquire an EBOV infection involve direct contact with the blood, vomit, sweat or stool of a person with advanced Ebola virus disease (EVD). But what is direct contact? What is an “airborne” route? For that matter what is an aerosol and what role do aerosols play in spreading EVD? How is an aerosol different from a droplet spray? Can droplets carry EBOV through the air?

Direct contact includes physical touch but also contact with infectious droplets; the contact is directly from one human to the next, rather than indirectly via an intermediate object or a lingering cloud of infectious particles. You cannot catch EVD by an airborne route, but you may from droplet sprays. Wait, what?? This is where a simple definition becomes really important.

(Continue . . . )