Khaberni - With the drop in temperature and the decrease in sunlight hours, the same scenario repeats every year: coughing, sneezing, fever, and body aches, signaling the start of the flu season.
Although this pattern has become familiar, the exact scientific reason behind the spread of illness in the winter remained obscure for a long time.
Over the past five years, this puzzle has begun to unravel, thanks to recent research indicating that the critical factor is not only related to human behavior or weakened immunity but also to the properties of the air we breathe, specifically the decrease in its humidity during winter.
Flu infections are estimated annually in the millions globally, while complications from the illness claim the lives of hundreds of thousands. The danger of the virus, according to Jean Metz from the University of Bristol, lies in its rapid ability to mutate, making the antibodies formed by the body in a previous season unable to recognize the new strain. She adds that this constant change “weakens acquired immunity and complicates the development of effective vaccines that a sufficient number of people would accept.”
For years, explanations focused on behavioral factors, such as spending more time indoors in crowded places during winter, or on physiological factors, such as weakened immune systems due to a lack of vitamin “D” from reduced sun exposure, or the constricting of blood vessels in the nose when inhaling cold air, which limits the arrival of immune cells to the mucous membranes.
However, these explanations were not sufficient. According to recent studies led by Jeffrey Shaman from Columbia University, the most important factor is dry air. According to the laws of physics, cold air carries less water vapor, leading to reduced humidity, creating an ideal environment for the influenza virus to survive and spread.
Shaman points out that analyzing climate and health data spanning over 30 years has shown that influenza waves often follow a significant drop in air humidity. Laboratory experiments on animals have also shown that the virus struggles to spread in humid conditions, whereas it transmits much faster in dry air.
The paradox lies in the fact that humidity, typically associated with feeling ill, could be a protective factor. In humid air, droplets from sneezes and coughs remain comparatively large and fall quickly, while in dry air they break down into fine particles that remain suspended for hours or even days, increasing the chances of inhalation. Additionally, water vapor itself may weaken the virus by affecting its chemical structure, while it remains active for longer durations in dry conditions.
These findings have opened the door to relatively simple solutions. Tyler Quib, who worked at the “Mayo Clinic,” estimated that running air humidifiers for just one hour in schools could reduce airborne viruses by about 30%.
He says that implementing this idea in places like hospital waiting rooms or public transportation could limit widespread outbreaks, reduce lost work and school days, and cut health care costs.
However, Shaman also warns against excessive use of humidification, noting that “high humidity could also facilitate the growth of other pathogens, such as mold, so these measures must be handled with caution.”
In conclusion, the scientists affirm that vaccines and maintaining personal hygiene remain the first line of defense against influenza, while carefully managed air humidity can be an additional weapon in combating a virus that rapidly changes and spreads.
