flu might be spread by breathing, speaking

An American study reveals the staggering spread of the virus in the air.

It is a little late to get vaccinated against the flu but at least we can try to avoid it. Dodging the flu is probably more difficult than previously thought. Indeed, bypassing patients who cough is probably not enough to avoid inhaling viral particles.

American researchers, whose work has just been published in the advanced edition of the Proceedings of the US National Academy of Sciences (Pnas) add some valuable information to existing recommendations. They realized that even without coughing, a sick person who breathes and speaks spreads the virus around him.

The researchers asked 142 people to breathe normally for 30 minutes in a device that collected air around them. The volunteers could of course cough or sneeze, and they also had to recite the alphabet three times during this half-hour.

The participants all had influenza, confirmed by specimens, whose symptoms had appeared for one to three days. This period corresponds to that of maximum contagiousness in case of contamination. 

To enter the study, volunteers recruited from 355 students with signs of respiratory infections had to have either a rapid diagnostic test (from a nasopharyngeal sample) indicating flu, a temperature above 37.8 ° C, with an irritated cough or throat.

Only one in three patients have fever and muscle aches

The symptoms of the flu are numerous. In a study conducted in Hong Kong seven years ago, three-quarters of influenza patients had signs of rhinitis (congested nose, runny nose), two-thirds coughed, half had sore throats and headache and only one in three patients with fever and muscle pain (myalgia).

Among the particles expelled by cough, there are droplets of varying sizes. Three years ago, a team from Massachusetts Institute of Technology (MIT) in Boston showed that the cloud of droplets and gases that form when someone coughs can spread widely. While it was thought that the smallest droplets did not go beyond one meter, the MIT researchers discovered that droplets could go up to six meters away, carried by the cloud! And as the warm moist air rises and diffuses widely, a patient quickly contaminates the space where he is confined.

The new Pnas study confirms this potential for aerial dissemination of viral particles, since 39% of aerosol samples (finest droplets, less than 5 micrometers) were found in the virus, but most of them were collected in half of the samples. the volunteers had neither coughed nor sneezed during the 30 minutes of the experiment.  Researchers were surprised, because usually  the cough  carries the virus.

Another surprise, the presence of virus in the nose has not, apparently, played a large role in the aerial dissemination of viruses. "This is why," the researchers write, "we can conclude that the airways of the head (nose, throat, Ed) are only a small contribution to the production of aerosolized viruses and that this comes from the 'lung infection.'

They also note that "women tend to cough for a lower viral load than men". And cough more frequently at equivalent viral load. "It could be that women have a more sensitive cough reflex," they say.

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flu might be spread by breathing, speaking