Cold and Flu is More Common During Winter Season: Here’s Why

Cold air is associated with increased viral infection because you’ve essentially lost half of your immunity just by that small drop in temperature.

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Previous in vitro studies conducted using human tissue in the lab was not carried out inside someone’s actual nose. Therefore, it is necessary to confirm these in vitro study findings in vivo.
A respiratory virus or bacteria invades the nose, the main point of entry into the body. Immediately, the front of the nose detects the germ, well before the back of the nose is aware of the intruder.

At that point, cells lining the nose immediately begin creating billions of simple copies of themselves called extracellular vesicle, or EVs. EVs can’t divide as cells can, but they are like little mini versions of cells specifically designed to go and kill these viruses.

EVs act as decoys, so now when you inhale a virus, the virus sticks to these decoys instead of sticking to the cells. Those are then expelled by the cells into nasal mucus, where they stop invading germs before they can get to their destinations and multiply.

This is one of, not the only parts of the immune system that leaves your body to go fight the bacteria and viruses before they get into the body. Once created and dispersed out into nasal secretions, the billions of EVs then start to swarm the marauding germs.

Protective Role of Nose in Colds and Flu

When under a virus attack, the nose increases the production of extracellular vesicles by 160%. There were additional differences: EVs had many more receptors on their surface than original cells, thus boosting the virus-stopping ability of the billions of extracellular vesicles in the nose.

These receptors as little arms that are sticking out, trying to grab onto the viral particles as you breathe them in. They found each vesicle has up to 20 times more receptors on the surface, making them super sticky.

Cells in the body also contain a viral killer called micro RNA, which attacks invading germs. Yet EVs in the nose contained 13 times more micro RNA sequences than normal cells.

What Happens to Immune System in Nose When Cold Weather Hits?

To find out this, researchers exposed four study participants to 15 minutes of 40-degree Fahrenheit (4.4-degree-Celsius) temperatures and then measured conditions inside their nasal cavities.

They found that when you’re exposed to cold air, the temperature in your nose can drop by as much as 9 degrees Fahrenheit. And that’s enough to exhibit its immune power. That little bit of coldness in the tip of the nose was enough to take nearly 42% of the extracellular vesicles out of the fight (1^✔ ✔Trusted Source
Cold exposure impairs extracellular vesicle swarm-mediated nasal antiviral immunity

Go to source).

Keeping Nose Warmer Prevents Colds and Flu

Keeping your intranasal environment warmer can maintain your stronger immune defenses against viruses. Wearing masks can help. These will prevent the viruses from directly entering your nose as well as keep your nose warmer (2^✔ ✔Trusted Source
Facial Skin Temperature and Discomfort When Wearing Protective Face Masks: Thermal Infrared Imaging Evaluation and Hands Moving the Mask

Go to source

).

The warmer you can keep the intranasal environment, the better this innate immune defense mechanism will be able to work. This may be yet another reason to wear masks.

In the future, researchers expect the development of topical nasal medications built upon this scientific revelation, to reduce the high infection rate in cold weather.

References

1. Cold exposure impairs extracellular vesicle swarm-mediated nasal antiviral immunity(https://www.jacionline.org/article/S0091-6749(22)01423-3/fulltext)
2. Facial Skin Temperature and Discomfort When Wearing Protective Face Masks: Thermal Infrared Imaging Evaluation and Hands Moving the Mask(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7369838/)

Source: Medindia