pediatric housecalls Robert R. Jarrett M.D. M.B.A. FAAP

Influenza Virus Spreads Even Without Coughing

I bet you feel pretty safe around someone with the “flu” if you don’t touch them, they don’t cough or sneeze and you stand at least six feet away. I know I always have and most others I know have as well. Not so!

In an absolutely amazing new study some infectious disease experts have found that those little viral beasties can get you even six feet away! That was as far as they tested, so those suckers might even go farther.

Pretty much until now we thought that influenza viral particles hitched a ride on large particle droplets when the patient sneezed or coughed. They don’t carry all that far due to their size and gravity. Instead however, they seem to be carried on sub-micron particles released into the air with simple talking and breathing.

The study done at Wake-Forest School of Medicine in North Carolina, during the 2010-2011 influenza season, was just (Jan 31) published in the Clinical Infectious Diseases journal and raises questions about the World Health Organization (WHO) and Centers for Disease Control (CDC) advice that face masks block large-particle droplets enough for medical personnel.

They studied 94 patients who came to the Emergency Department (ED) or were admitted to the hospital with flu-LIKE illnesses. They tested all of them for Influenza Virus and found that the diagnosis was correct in about two-thirds of them, 61 (65%). And, here’s the interesting part, they set up what they call “quantitative impaction air samples” gathering devices at 1 foot, 3 feet and 6 feet from the patients head while they went about giving routine care.

Of the 61 positive patients about half, 42% (26), actually emitted virus into the room air and some (5) even were “super-emitters” – 35 times what the “normal” emitters shed. And, believe it or not, the air samples from all the “emitters” exceeded the dosing level where 50% of normal humans become infected – at all locations, no matter how far away. So, even though the article said “up to” six feet, it only looks to me like they can say “at least” six feet.

So, which patients are likely to be an “emitter” – they couldn’t tell for sure. All they could say was that “emitters” were likely to be experiencing a more severe level of illness, less able to go about daily living chores but surprisingly less likely to report having chills.

They did find both large particles and small particles less than 4.7 microns. And the small particles were released in patients who didn’t even cough or sneeze – only breathed and talked!

What medical professional’s are stuck with now is: How do we protect ourselves from the airborne viruses? Simple masks don’t filter out particles that small. A leading pediatrician, Caroline Hall MD from the University of Rochester, wrote an accompanying editorial to the report trying to delineate some possibilities.

She stated pretty much what is obvious to most pediatricians: the N95 type respirators (think Andromeda Strain) are expensive and using them on all potentially influenza-positive patients isn’t even close to “being feasible.”

What we do have is a better understanding of just how little “covering your mouth when you cough” actually does to protect against influenza. That makes mandating influenza immunization’s for all health care workers even more important as well as following meticulously what guidelines we do have.

[Clinical Infectious Diseases. Published online January 31, 2013.]

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