Breathing Out Viral Aerosols

"We found that flu cases contaminated the air around them with infectious virus just by breathing, without coughing or sneezing."
"People with flu generate infectious aerosols even when they are not coughing, and especially during the first days of illness. So when someone is coming down with influenza, they should go home and not remain in the workplace and infect others."
Donald Milton, professor of environmental health, University of Maryland

"The study findings suggest that keeping surfaces clean, washing our hands all the time and avoiding people who are coughing does not provide complete protection from getting the flu."
"Staying home and out of public spaces could make a difference in the spread of the influenza virus."
Sheryl Ehrman, chemical and biomolecular engineering professor, San Jose State University

Lead researcher Donald Milton said, “people with flu generate infectious aerosols even when they are not coughing, and especially during the first days of illness.” Gregory Bull / THE ASSOCIATED PRESS

A new paper resulting from a study of influenza's transmission recently published in the Proceedings of the National Academy of Sciences, more or less puts to rest the common wisdom that sneezing and coughing are the primary methods through which aerosol sprays containing the flu virus contaminate an environment. This winter's flu season is turning out to be one of those in which an especially virulent flu is going the rounds. The inoculation serum has proven not to be as effective as hoped; in fact, particularly ineffective. But, as scientists shrug, better than nothing.

What researchers discovered through this study is that it provides "overwhelming evidence" that tiny droplets of the flu virus float on the atmosphere as an aerosol and remain suspended there for a lengthy period, and they do this through the normal human mechanism of simply breathing; no coughs, no sneezes required to propel the virus. What has been taken for granted up to now -- that transmission takes place when droplets are propelled by coughs and sneezes -- is somewhat more complex.

Of course, those affected can also spread the virus by touch, contaminating surfaces, or sharing food, but these contacts no longer represent a meaningful measure of transmission. The study by a University of Maryland-led team of researchers makes it obvious that those affected need only breathe in and out and they've distributed the virus freely through that simple mechanism of existence. The viral load of the flu virus expelled through natural breathing, speaking, coughing and sneezing was measured by scientists to determine the surprising results.

And the results are important in our understanding of how such viruses spread. So that the public can be advised how best to react for the purpose of reducing the spread of the flu and in the process helping to control the possibility of epidemics and pandemics. For the research, 355 volunteers with symptoms, identifiable as acute respiratory illness were screened. In the process 142 of that number were isolated with confirmed influenza infection and they were asked to provide several types of breath samples over several days of their illness.

Viral loads were measured by the scientists from the samples provided when patients were breathing, speaking, spontaneously coughing and sneezing. The relative infectivity was then assessed. Influenza patients did not commonly sneeze, the researchers discovered, but when they did, they also coughed yet despite the force of a sneeze, the viral load of the flu virus was roughly similar to a cough leading to the conclusion that sneezing is not, after all, to be considered a significant transmission method for the flu.

Researchers say that simply breathing out is enough to spread the flu virus. Medical News Today

 

In sampling sessions where no coughs were observed, on the other hand, the virus was detected in 48 percent of samples and as well, infectious virus was discovered in 39 percent of fine-aerosol samples taken in 30 minutes of normal breathing, leading to the conclusion that a significant fraction of influenza cases present at risk for airborne transmission in the absence of coughing or sneezing.

Men generated viral shedding from coughing quite a bit more than did women, and there was greater viral shedding through the mechanics of simply breathing taken from overweight and obese participants. Moreover, since a rapid decline of the viral load was found in samples representing the last of three days of collection, the intimation was that as the virus progresses in a patient, there is a decreased airborne contagion.

If people take the familiar caution to remain at home at the first symptoms of flu onset seriously, the potential of infecting other people is vastly reduced. In the same token, as the days of infection mature, it seems the risk of contaminating others is also reduced. Of course, in the throes of flu symptoms there is less desire to leave home and return to work -- until such time as the symptoms have fully abated and the patient feels relief; at the same time becoming less contagious.