Respiratory viruses love winter. These pathogens thrive in the cold and travel more easily from host to host in dry air.
“When cold outdoor air with little moisture is heated indoors, the relative humidity of the air drops to about 20 percent,” Akiko Iwasaki, an immunobiologist at Yale University, said in a statement.
“This dry air provides a clear pathway for airborne viruses.”
Relative humidity (RH) is a measure of how full the air is with a water valve. So in a room with a relative humidity of 40 percent, the air retains 40 percent of the total humidity it can fully retain.
The drier the air, the lower the relative humidity, and the easier it is for viruses – including the coronavirus – to spread.
That’s why Linsey Marr, an aerosol researcher from Virginia Tech University who studies the spread of coronavirus, recommends using a humidifier in your home.
“You could invest in a humidifier and set it up to keep the humidity above 40 per cent but below 60 per cent in the winter,” she told Business Insider. good under these conditions, and your immune response works better than when the air is dry. “
Humidity and temperature affect how the coronavirus spreads
Research shows that the coronavirus spreads more easily when temperatures and humidity are low.
A study in July by aerosol research scientist Ajit Ahlawat and his colleagues found that the chances of the coronavirus becoming infected in dry places are higher than in humid areas.
That’s because coronavirus particles in drier, more humid air contain less moisture and thus stay farther away. That makes them more likely to be introduced and infectious to someone new.
In addition, coronavirus particles become more stable as temperatures and humidity levels go down, helping them stay stable enough to introduce new hosts when they arrive.
Additionally, like the flu, the coronavirus is carved into a fat layer called a lipid envelope that helps it survive from one person to the next. This broom dries faster at higher temperatures.
Wet air can work against the protective layer by causing damage to the structure of the lipid envelope, triggering the action of the virus.
“To control indoor airborne coronavirus spread, especially in poorly ventilated indoor areas such as hospitals, schools, and public buildings, we recommend the use of humidifiers,” Ahlawat told Business Insider.
Like Marr, it recommends an internal RH of between 40 percent and 60 percent.
Higher temperatures can also prevent the virus from spreading through the surface, although this type of transmission is rare.
A study published in June showed that warmer weather can determine how long the coronavirus stays on the surface.
Relative humidity of 40 to 60 percent also benefits our immune systems
This fall, Iwasaki helped launch a petition calling on the World Health Organization to set guidelines for indoor humidity levels. It calls 40-60 percent RH a “sweet spot,” because indoor air in that area “allows our nose and throat to maintain strong immune responses” against many viruses.
The built-in defenses of our immune systems – such as the mucus in our noses – work best when the air is wetter.
That’s because mucus coats the hair-like flexible tissue called cilia that erupt from cells in our airways (picture them as moving seaweed underwater). Cilia is responsible for capturing viral particles that try to float into our lungs.
According to a recent study by Iwasaki and her colleagues, low humidity dries that mucus; as the lubricating mucus dries, these immune cilia fall flat, preventing their ability to outgrow viruses.
But experts warn against excessive humidity
It is essential not to overdo it, however.
“Be extra careful not to get above 65 percent, because that can promote mold growth,” Marr said. The resulting mold can lead to asthma, and many people are allergic to mold spores.
Ahlawat also said a humidity level above 60 percent would be “too uncomfortable for indoor residents.”
Numbers to one side, some experts oppose the use of humidifiers at all as a way to reduce viral spread.
“This is an unproven approach and has the potential for real adverse effects,” Donald Milton, a professor of environmental health at the University of Maryland, told Elemental in November. “I don’t recommend it.”
Marr also warned that a crushing machine should not be used as a panacea to stop the virus.
“The most important things are wearing a mask, maintaining speed, ensuring good ventilation and / or air filtration, and washing your hands,” she said.
This article was originally published by Business Insider.
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