A new study into how influenza spreads has found that you aren't safe from infection even when 6 feet from someone with influenza - and the infected person doesn't even have to be coughing or sneezing. Just talking and breathing releases small particles that aren't filtered out by surgical masks. About 20% of the studied patients were super-shedders, releasing more than 10 times as many particles as other patients, though these individuals were recognisable sicker.
Medscape Medical News
medscape.com/viewarticle/77...
Paper
jid.oxfordjournals.org/cont...
Editorial
jid.oxfordjournals.org/cont...
Note that this study detected the influenza virus in air samples using polymerase chain reaction - a technique of 'amplifying' genetic material. It didn't show that influenza virus in the particles detected was viable and infectious or that transmission to others actually occurred. No doubt it would be very hard to prove what exposure actually infected a healthcare professional contracting influenza given the multiple exposures experienced.
Some quotes, many rather disturbing:
"Bischoff and colleagues demonstrated that surgical masks with or without eye protection were ineffective as a barrier against exposure to influenza virus in small particles (diameter, <5 µm). N95 respirators were required for an appreciable reduction (by 40%) in influenza virus transmission, and if eye protection was added, the transmission was reduced by 80%."
"... individuals with influenza may be asymptomatic before the onset of clinical illness, and some may continue to have influenza virus detectable in their nasopharyngeal secretions long after signs of clinical illness have subsided."
"The possibility of airborne spread of potentially infectious doses of influenza virus raises the specter of direct inoculation of the lower respiratory tract with quantities of virus that can cause more severe illness, which is possible with very low doses."
I particularly like Caroline Breese Hall's closing quotes in the Editorial:
"This study not only adds to our understanding of these risks, but helps define the questions that still need answering."
"Centuries of scientific observation and of prophets wise have shown us what we know defines what we know not, and there is where our future lies."
"Dr. Hall died on December 10, 2012, at the age of 73 years. She was internationally known for her work in pediatric infectious diseases."
So what does this all mean to us with low immunity and with a poor response to influenza vaccinations? Assuming that the influenza viruses contained in the small droplets that spread so widely were indeed viable (unfortunately a safe assumption), wearing a surgical mask and eye protection will give you SOME LIMITED protection, but you are probably better off avoiding crows and encouraging those with which you associate frequently to have the influenza vaccination.
Neil
