While the K flu variant has shaken up epidemiological forecasts this winter with an early peak in France, the question of modes of transmission remains at the heart of concerns. An original clinical study sheds surprising light. For the first time, scientists brought together naturally infected people and healthy volunteers in a controlled environment.
Cough: the real driver of infection
For several days, 11 healthy adults shared the daily lives of 5 flu-stricken students in an enclosed space. All while even exchanging objects (pens, tablets). Result: no contamination was recorded.
The first observation of this experiment is counterintuitive. Having a high viral load would not necessarily be enough to contaminate others. If the sick students had a lot of virus in their nasal secretions, they barely coughed. A detail that changes everything.
“Airborne transmission of influenza, primarily via aerosols and droplets, can be significantly reduced by several environmental, behavioral and immunological factors, as demonstrated in the recent University of Maryland study. Limited coughing among patients greatly reduces the emission of viral particles into the air. And this, even if the virus is present in quantity in the nasal passages. specifies Dr. Gérald Kierzek, emergency physician and medical director of True Medical.
Conversely, as soon as the symptoms become more severe, the risk explodes.
“Frequent coughing projects droplets and aerosols rich in viruses, drastically increasing the risk indoors.
he specifies.
Ventilation, the secret weapon against viruses
The other key to this preventive success lies in the quality of the air in the hotel room used for the experiment. The air was constantly circulated there by a heater and a dehumidifier. This helped dilute the viral load.
“Rapid renewal of the air, by mechanical ventilation, opening windows or purifiers, dilutes the viral particles. This prevents their accumulation in enclosed spaces. confirms Dr. Kierzek again.
He adds that “the use of dehumidifiers or heaters promotes air circulation which disperses the small quantities of viruses emitted, as observed in hotel experiments without contamination“.
According to him, it is precisely “stagnant air, without circulation or renewal, which allows the accumulation of viruses and short distance face-to-face exposures.
Immunity and barrier gestures, an essential shield
Finally, the study highlights that middle-aged adults are overall less likely to contract the flu than children or young adults. This natural resistance, coupled with rigorous hygiene measures, completes the protection system.
For Dr Gérald Kierzek, the control strategy must be global. “Vaccination strengthens immunity, particularly in exposed adults, reducing susceptibility to infection despite prolonged proximity“. It also recalls the importance of individual behavior.
“Wearing a mask, coughing into your elbow and throwing away used tissues limit the projection of droplets. Frequent hand washing and avoidance of close contact complement these effects by reducing mixed pathways, both airborne and by contact.”
In conclusion, if promiscuity in enclosed and poorly ventilated places such as transport or offices remains the main risk factor, this study proves that controlling air quality and good health (mask and hygiene in case of cough) are extremely effective defenses.